Backlight module with mjt led and backlight unit incluing the same

ABSTRACT

A backlight unit including a backlight module and a backlight control module. The backlight module includes a printed circuit board including blocks, and light emitting diode (LED) chips disposed on the blocks, and the backlight control module is configured to perform a dimming control of the LED chips. Each of the LED chips includes light emitting cells spaced apart from each other, each of the light emitting cells including a lower semiconductor layer, an upper semiconductor layer, and an active layer therebewteen, in which the lower semiconductor layers are partially exposed, connection structures electrically connecting the light emitting cells to each other, and an insulation layer disposed between the light emitting cells and the connection structures, the insulation layer covering a portion of the exposed lower semiconductor layers and having a width wider than the connection structures.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/812,437, filed on Jul. 29, 2015, which is a continuation-in-part ofU.S. patent application Ser. No. 14/339,051, filed on Jul. 23, 2014, andclaims priority from and the benefit of Korean Patent Application No.10-2014-0026574, filed on Mar. 6, 2014, and Korean Patent ApplicationNo. 10-2015-0095536, filed on Jul. 3, 2015, all of which are herebyincorporated by reference for all purposes as if fully set forth herein.

BACKGROUND

Field

The present disclosure relates to a backlight module using a multijunction technology (MJT) light emitting diode (LED) and a backlightunit including the same. More particularly, the present disclosurerelates to a backlight module which employs an MJT LED configured toincrease an effective light emitting area of each of light emittingcells to allow operation at low current, and a backlight unit includingthe same.

Description of the Background

A liquid crystal display creates an image by controlling transmittanceof a backlight light source. Although a cold cathode fluorescent lamp(CCFL) has generally been used as a backlight light source in therelated art, light emitting diodes (hereinafter, LEDs) are beingrecently used due to various advantages such as low power consumption,long lifespan, eco-friendliness, and the like.

Backlight units can be classified into edge type backlight units anddirect type backlight units according to the locations of LEDs forbacklighting a liquid crystal display. In an edge type backlight unit,with LEDs arranged as light sources on a side surface of a light guideplate, light entering the light guide plate from the light sources isused for backlighting of a liquid crystal panel. Thus, the edge typebacklight unit can reduce the number of LEDs and does not require strictcontrol of quality deviation among the LEDs, thereby enablingmanufacture of low power consumption products, which is advantageous interms of cost. However, in the edge type backlight unit it is difficultto overcome contrast between a corner area and a central area of theliquid crystal display and it is difficult to create high qualityimages.

Alternatively, a direct type backlight unit is placed under a liquidcrystal panel and allows light emitted from a surface light source,which has substantially the same area as that of the liquid crystalpanel, to directly illuminate a front side of the liquid crystal panel.The direct type backlight unit can overcome contrast difference betweena corner area and a central area of the liquid crystal display and canachieve high quality images.

However, in the direct type backlight unit, if each of the LEDs does notilluminate a relatively wide area for backlighting, a number of LEDsmust be densely arranged, thereby causing increase in power consumption.Moreover, deviation in quality between the LEDs can make it difficult tosecure a uniform screen illumination due to uneven backlighting of aliquid crystal panel.

Particularly, with the increasing size of liquid crystal panels, thesize of the direct type backlight unit is also increased, therebycausing deterioration in stability or reliability of the direct typebacklight unit. Specifically, since the LED backlight unit controls theoperating current supplied to a plurality of LED groups, that is, LEDarrays, through a plurality of LED drive circuits, the number of LEDdrive circuits and the number of LED corresponding arrays aresignificantly increased as the size of the LED backlight unit increases.As a result, a disconnection can occur between the plurality of LEDs orLED arrays arranged adjacent each other, whereby the drive circuits aredamaged due to overcurrent, overvoltage, or overheating, therebydeteriorating the stability and reliability of the backlight unit.

FIG. 1 is a configuration block diagram of a typical backlight unitusing LEDs in the related art. With reference to FIG. 1, problems of therelated art will be described in more detail. As shown in FIG. 1, atypical backlight unit 1 includes a backlight control module 2 and abacklight module 5.

The backlight control module 2 includes an operating power generator 3,which generates/outputs DC power based on input voltage Vin input froman external power source, and an operation controller 4 controllingoperation of each of a plurality of LED arrays 6 a-6 n constituting thebacklight module 5. The operating power generator 3 generally generatesDC voltages such as 12V, 24V, 48V, and the like as operating power.

The backlight module 5 includes a plurality of LED arrays 6 a-6 n eachformed by connecting a plurality of LEDs in series, and an optical unit(not shown) for enhancing efficacy of light emitted from the pluralityof LED arrays 6 a-6 n. In FIG. 1, the backlight unit 5 includes n LEDarrays 6 a-6 n connected to each other in parallel and each includingfive LEDs connected to each other in series. Here, since each of theLEDs used in the backlight unit generally has a forward voltage level inthe range from 3V to 6.5V and is difficult to individuallycontrol/operate when connected to the operating power generator 3,plural LEDs are connected to each other in series to constitute LEDarrays such that each of the LED arrays can be operated/controlled. Insuch a typical backlight unit 1 in the related art, the operationcontroller 4 is configured to control brightness of all of the LEDarrays 6 a-6 n constituting the backlight module 5 through pulse widthmodulation (PWM) control with respect to the operating power supplied tothe backlight module 5 in response to an external dimming signal (Dim).Otherwise, in such a typical backlight unit 1, the operation controller4 adjusts the operating current flowing through a specific LED arrayamong the n LED arrays 6 a-6 n in response to an external dimming signal(Dim) to control brightness of the specific LED array.

LEDs used in such a typical backlight unit 1 are generally single-cellLEDs capable of being operated at low voltage and high current. Forexample, such a single-cell LED has an operating voltage of 3.6V and canbe operated at an operating current of 250-500 mA. Thus, in order tocontrol operation of the backlight module 5 constituted by suchsingle-cell LEDs, peripheral circuits including the operation controller4 in the related art must be constituted by large capacity electronicdevices capable of handling large current, thereby causing increase inmanufacturing costs of the backlight unit 1. In addition, the peripheralcircuits including the operation controller 4 are damaged due to thehigh current operation characteristics of the aforementioned typicalsingle-cell LEDs, thereby causing deterioration in stability orreliability of the backlight unit 1. In addition, the high currentoperation characteristics of the single-cell LEDs cause an increase inpower consumption and a droop phenomenon.

SUMMARY

The present disclosure is aimed at providing a backlight module whichcan be operated at low current using an MJT LED including a plurality oflight emitting cells and a backlight unit including the same.

In addition, the present disclosure is aimed at providing an MJT LEDchip, which can increase an effective light emitting area of a lightemitting cell, and a method of manufacturing the same.

Further, the present invention is aimed at providing a backlight unit,which allows a backlight module to be operated at low current using theaforementioned MJT LED, thereby improving stability and reliability ofdrive circuits for controlling operation of the backlight module, andenabling reduction in manufacturing costs.

Further, the present disclosure is aimed at providing a backlight unit,which allows a backlight module to be operated at low current using theaforementioned MJT LED, thereby improving power efficiency and luminousefficacy while preventing a droop phenomenon due to operation at highcurrent.

Further, the present disclosure is aimed at providing a backlight unit,in which a backlight module is constituted by MJT LEDs, therebyminimizing the number of LEDs while enabling individual control of theMJT LEDs.

The above and other objects and advantageous effects of the presentdisclosure can be obtained by the following features of the presentdisclosure.

In accordance with one aspect of the present disclosure, a backlightmodule includes a printed circuit board; a plurality of MJT LEDsdisposed on the printed circuit board; and a plurality of opticalmembers disposed on the MJT LEDs or the printed circuit board so as tocorrespond to the MJT LEDs and each including a light incident facethrough which light emitted from the corresponding MJT LED enters theoptical member and a light exit face through which light exits theoptical member at a wider beam angle than that of the corresponding MJTLED, wherein each of the MJT LEDs includes a first light emitting celland a second light emitting cell separated from each other on a growthsubstrate; a first transparent electrode layer placed on the first lightemitting cell and electrically connected to the first light emittingcell; a current blocking layer placed between the first light emittingcell and the first transparent electrode layer and separating a portionof the first transparent electrode layer from the first light emittingcell; an interconnection line electrically connecting the first lightemitting cell to the second light emitting cell; and an insulation layerseparating the interconnection line from a side surface of the firstlight emitting cell. Here, the second light emitting cell has a slantedside surface; and the interconnection line includes a first connectionsection for electrical connection to the first light emitting cell and asecond connection section for electrical connection to the second lightemitting cell. The first connection section contacts the firsttransparent electrode layer within an upper area of the current blockinglayer, and the second connection section contacts the slanted sidesurface of the second light emitting cell.

In one aspect, each of the MJT LEDs includes first to N-th lightemitting cells (N being a natural number of 2 or more), and the N-thlight emitting cell may be electrically connected to a (N-1)th lightemitting cell using the same structure as a connection structure betweenthe first light emitting cell and a second light emitting cell.

In one aspect, the first to N-th light emitting cells are connected toeach other in series and each operated by an operating voltage of 2.5Vto 4 V. Here, each of the MJT LEDs may be operated at an operatingvoltage of at least 10 V or more.

In one aspect, each of the MJT LEDs includes three light emitting cellseach being operated at an operating voltage of 3V to 3.6V, and isoperated at an operating voltage of 12V to 14V.

In one aspect, the light exit face includes a concave section formednear a central axis of the optical member and a convex section extendingfrom the concave section and separated from the central axis of theoptical member.

In one aspect, the light exit face includes a total reflection surfaceso as to form an apex under the central axis of the optical member.

In one aspect, the light incident face includes an opening formed nearthe central axis of the optical member, and the height of the opening is1.5 times or more a width thereof.

In one aspect, each of the optical members has a light scatteringpattern formed on at least a portion of a bottom surface facing theprinted circuit board.

In one aspect, each of the optical members includes a lower surfacehaving a concave section, through which light emitted from the MJT LEDenters the optical member; and an upper surface through which lightentering the optical member through the concave section exits theoptical member. Here, the upper surface includes a concave surfaceplaced at the central axis of the optical member, and the concavesection of the lower surface includes at least one of a perpendicularsurface relative to the central axis and a downwardly convex surface,and the at least one of the perpendicular surface relative to thecentral axis and the downwardly convex surface may be placed within anarrower area than an area for an entrance of the concave section.

In one aspect, the upper surface and the concave section of the opticalmember form a mirror symmetry structure relative to a plane passingthrough the central axis of the optical member.

In one aspect, the upper surface and the concave section of the opticalmember form a rotational body shape relative to the central axis of theoptical member.

In one aspect, each of the optical members has a light scatteringpattern formed on the at least one of the perpendicular surface relativeto the central axis and the downwardly convex surface within the concavesection of the lower surface and on a surface closer to the central axisthan the at least one surface.

In one aspect, each of the optical members has a light scatteringpattern formed on the concave surface of the upper surface.

In one aspect, each of the optical members further includes a materiallayer having a different index of refraction than the optical member onthe at least one of the perpendicular surface relative to the centralaxis and the downwardly convex surface within the concave section of thelower surface and on a surface closer to the central axis than the atleast one surface.

In one aspect, each of the optical members further includes a materiallayer having a different index of refraction than the optical member onthe concave surface of the upper surface.

In one aspect, the at least one of the perpendicular surface relative tothe central axis and the downwardly convex surface is defined within anarrower area than an area surrounded by an inflection curve at whichthe concave surface of the upper surface meets the convex surfacethereof.

In one aspect, the at least one of the perpendicular surface relative tothe central axis and the downwardly convex surface is defined within anarrower area than an area of a light exit face of the light emittingdiode.

In one aspect, each of the optical members further includes a flangeconnecting the upper surface and the lower surface and the at least oneof the perpendicular surface relative to the central axis and thedownwardly convex surface within the concave section is placed above theflange.

In one aspect, each of the optical members has an optical axis L, alight incident section, and a light exit face, and is formed of amaterial, the index of refraction of which is higher than that of amaterial adjoining the light incident section and that of a materialadjoining the light exit face.

In one aspect, the light incident section is formed such that theshortest distance from a point (p) on the optical axis L to an apex ofthe light incident section is greater than the shortest distance (a)from the point (p) to a side surface of the light incident sectionwithin an angle of 50° or less from the optical axis L.

In one aspect, an upper center of the light exit face is formed of aflat surface or a convex curve.

In one aspect, the light incident section includes a lower entranceplaced adjacent the light emitting diode and having a circular shape,and has a shape gradually converging to the apex while maintaining acircular shape.

In one aspect, the light incident section has a height which is 1.5times greater than a radius of the lower entrance.

In one aspect, the material adjoining the light incident section is air.

In one aspect, the material adjoining the light exit face is air.

In one aspect, the optical members are formed of a resin or glass.

In accordance with another aspect of the present disclosure, a backlightunit includes the aforementioned backlight module; and a backlightcontrol module supplying DC operating voltage to the plurality of MJTLEDs within the backlight module and independently controlling operationof each of the plurality of MJT LEDs.

In one aspect, the backlight control module supplies the DC operatingvoltage to each of the plurality of MJT LEDs within the backlightmodule, and performs pulse width modulation control with respect to theDC operating voltage supplied to at least one MJT LED among theplurality of MJT LEDs in response to a dimming signal to perform dimmingcontrol of the at least one MJT LED.

In one aspect, the backlight control module allows independent detectionand control of operating current of each of the plurality of MJT LEDswithin the backlight module, and controls operating current of at leastone MJT LED among the plurality of MJT LEDs in response to a dimmingsignal to perform dimming control of the at least one MJT LED.

According to an exemplary embodiment of the present disclosure, there isprovided a backlight unit including: a printed circuit board includingblocks; a backlight module including multi junction technology (MJT)light emitting diodes(LEDs) respectively disposed on the blocks; and abacklight control module configured to provide an operating voltage tothe MJT LEDs within the backlight module, wherein each of the blocksincludes at least one of the MJT LEDs, and the backlight control moduleis configured to independently control an operation of each of the MJTLEDs.

The backlight control module may include an operating power generator;and an operation controller.

The operating power generator may be configured to independently providethe operating voltage to each of the MJT LEDs within the backlightmodule, and the operation controller may be configured to perform adimming control of at least one of the MJT LEDs by performing a pulsewidth modulation (PWM) control in response to a dimming signal of thebacklight control module.

The operation controller may be configured to generate a dimming controlsignal of which a pulse width is modulated or a duty ratio is modulated.

The operation controller may be configured to independently detect andcontrol an operating current of at least one of the MJT LEDs within thebacklight module.

The operation controller may be configured to perform a dimming controlof at least one of the MJT LEDs by controlling the operating current ofat least one of the MJT LEDs in response to a dimming signal of thebacklight control module.

An anode terminal of at least one of the MJT LEDs may be connected tothe operating power generator, and a cathode terminal of at least one ofthe MJT LEDs may be connected to the operation controller.

The backlight unit may further include an optical member disposed on theMJT LEDs or the printed circuit board so as to correspond to the MJTLEDs.

The optical member may include a light incident face through which lightemitted from the MJT LED enters and a light exit face through which thelight exits at a wider light directivity angle than a light directivityangle of the MJT LEDs.

of the backlight unit may include optical members, and each of theoptical members may be respectively disposed on one of the MJT LEDs.

The optical member may include a molded-resin on the MJT LEDs.

Each of the blocks may include one optical member.

Each of the blocks may have a horizontal length of 60 mm or less.

Each of the blocks may have a vertical length of 55 mm or less.

The blocks may include M×N blocks, and the blocks may constitute an M×Nmatrix arrangement.

At least one block of the blocks may include at least one of the MJTLEDs.

The MJT LEDs may be configured to include first to N-th light emittingcells (N is a natural number of 2 or greater), and the N-th lightemitting cell may be electrically connected to an N-1-th light emittingcell in the same structure as the first light emitting cell and a secondlight emitting cell are electrically connected to each other.

The first to N-th light emitting cells may be connected to each other inseries and are configured to be operated by an operating voltage of 2.5Vto 4V, and the MJT LEDs may be configured to be operated by theoperating voltage of at least 10V or greater.

The plurality of MJT LEDs may include: a first light emitting cell and asecond light emitting cell disposed on a growth substrate to be spacedapart from each other, each of the first light emitting cell and thesecond light emitting cell including a lower semiconductor layer, anupper semiconductor layer disposed on the lower semiconductor layer, andan active layer disposed between the lower semiconductor layer and theupper semiconductor layer; a first transparent electrode layer disposedon the first light emitting cell and electrically connected to the firstlight emitting cell; an interconnection line electrically connecting thefirst light emitting cell and the second light emitting cell to eachother; and an insulation layer spacing apart the interconnection linefrom a side surface of the first light emitting cell. Theinterconnection line has a first connection section for an electricalconnection to the first light emitting cell, and a second connectionsection for an electrical connection to the second light emitting cell,one surface of the lower semiconductor layer may include an exposedregion exposing the lower semiconductor layer, the first connectionsection may contact the first transparent electrode layer, and thesecond connection section may be electrically connected to the lowersemiconductor layer of the second light emitting cell through theexposed region.

A portion of the first transparent electrode layer may be connected tothe second light emitting cell.

The portion of the first transparent electrode layer may be disposed onthe first light emitting cell, between the first light emitting cell andthe second light emitting cell, and on a side surface of the lowersemiconductor layer of the second light emitting cell.

A width of a portion of the first transparent electrode layer disposedon the side surface of the lower semiconductor layer of the second lightemitting cell may be wider than a width of a portion of theinterconnection line disposed on the side surface of the lowersemiconductor layer of the second light emitting cell.

A width of a portion of the first transparent electrode layer disposedbetween the first light emitting cell and the second light emitting cellmay be wider than a width of a portion of the interconnection linedisposed between the first light emitting cell and the second lightemitting cell.

The first transparent electrode layer may space apart theinterconnection line from the insulation layer.

A portion of the insulation layer may be disposed on a portion of thegrowth substrate disposed between the first light emitting cell and thesecond light emitting cell.

The backlight unit may further include a current blocking layer disposedbetween the first light emitting cell and the first transparentelectrode layer to space apart a portion of the first transparentelectrode layer from the first light emitting cell.

The first transparent electrode layer may be disposed between the secondconnection section and the lower semiconductor layer of the second lightemitting cell.

The backlight unit may further include a floodlighting plate disposed onthe printed circuit board, wherein a distance between an upper surfaceof the printed circuit board and a lower surface of the floodlightingplate is 18 mm or more.

The operation controller may include a switch controller thatelectrically connects or insulates the MJT LEDs to and from each other.

The switch controller may connect the MJT LEDs in series and/or inparallel to each other.

The backlight module may include a phosphor and further includes awavelength conversion layer covering the MJT LEDs, and light emittedfrom the MJT LEDs to penetrate through the wavelength conversion layermay have a National Television System Committee (NTSC) colorreproduction ratio of 70% or greater.

As the number of light emitting cells within an MJT LED increases, anarea of a block associated with the MJT LED may decrease.

According to another exemplary embodiment of the present disclosure,there is provided a backlight unit including: a printed circuit boardincluding blocks; and a backlight module including multi junctiontechnology (MJT) light emitting diodes (LEDs) disposed on the pluralityof blocks; wherein the MJT LEDs include: a first light emitting cell anda second light emitting cell disposed on a growth substrate to be spacedapart from each other and each including a lower semiconductor layer, anupper semiconductor layer disposed on the lower semiconductor layer, andan active layer disposed between the lower semiconductor layer and theupper semiconductor layer; a first transparent electrode layer disposedon the first light emitting cell and electrically connected to the firstlight emitting cell; an interconnection line electrically connecting thefirst light emitting cell and the second light emitting cell to eachother; and an insulation layer spacing apart the interconnection linefrom a side surface of the first light emitting cell. Theinterconnection line has a first connection section for an electricalconnection to the first light emitting cell, and a second connectionsection for an electrical connection to the second light emitting cell,one surface of the lower semiconductor layer includes an exposed regionexposing the lower semiconductor layer, the first connection sectioncontacts the first transparent electrode layer, the second connectionsection is electrically connected to the lower semiconductor layer ofthe second light emitting cell through the exposed region, and anoperation of each of the MJT LEDs is configured to be independentlycontrolled.

A portion of the first transparent electrode layer may be connected tothe second light emitting cell.

The portion of the first transparent electrode layer may be disposed onthe first light emitting cell, between the first light emitting cell andthe second light emitting cell, and on a side surface of the lowersemiconductor layer of the second light emitting cell.

A width of a portion of the first transparent electrode layer disposedon the side surface of the lower semiconductor layer of the second lightemitting cell may be wider than a width of a portion of theinterconnection line disposed on the side surface of the lowersemiconductor layer of the second light emitting cell.

A width of a portion of the first transparent electrode layer disposedbetween the first light emitting cell and the second light emitting cellmay be wider than a width of a portion of the interconnection linedisposed between the first light emitting cell and the second lightemitting cell.

The first transparent electrode layer may space apart theinterconnection line from the insulation layer.

A portion of the insulation layer may be disposed on a portion of thegrowth substrate disposed between the first light emitting cell and thesecond light emitting cell.

The backlight unit may further include a current blocking layer disposedbetween the first light emitting cell and the first transparentelectrode layer to space apart a portion of the first transparentelectrode layer from the first light emitting cell.

The first transparent electrode layer may be disposed between the secondconnection section and the lower semiconductor layer of the second lightemitting cell.

According to embodiments of the present disclosure, the backlight moduleis fabricated using MJT LEDs having low current operationcharacteristics, thereby enabling low current operation of the backlightmodule and the backlight unit including the same.

In addition, according to the embodiments of the present disclosure, oneconnection section of the interconnection line electrically contacts aslanted side surface of light emitting cell, thereby increasing aneffective light emitting area of each of light emitting cells in an MJTLED chip.

Further, according to the embodiments of the present disclosure, it ispossible to enhance stability and reliability of drive circuits forcontrolling operation of the backlight module while reducingmanufacturing costs.

Further, according to the embodiments of the present disclosure, thebacklight unit has improved power efficiency and luminous efficacy, andcan prevent a droop phenomenon due to operation at high current.

Further, according to the embodiments of the present disclosure, it ispossible to minimize the number of LEDs constituting the backlightmodule and to allow individual operation of the MJT LEDs constitutingthe backlight module.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of the presentdisclosure will become apparent from the detailed description of thefollowing embodiments in conjunction with the accompanying drawings, inwhich:

FIG. 1 is a configuration block diagram of a typical backlight unitincluding LEDs in the related art;

FIG. 2 is a schematic block diagram of a backlight unit employing MJTLEDs according to one exemplary embodiment of the present disclosure;

FIG. 3 is a schematic sectional view of an MJT LED module according toone exemplary embodiment of the present disclosure;

FIG. 4 is a schematic perspective view of the MJT LED according to theone exemplary embodiment of the present disclosure;

FIG. 5 is a schematic plan view of an MJT LED chip according to oneexemplary embodiment of the present disclosure;

FIG. 6 is a schematic sectional view of the MJT LED chip taken alongline B-B of FIG. 5;

FIG. 7 to FIG. 13 are schematic sectional views illustrating a method offabricating an MJT LED chip according to one exemplary embodiment of thepresent disclosure;

FIG. 14 is a schematic sectional view of an MJT LED chip according toanother exemplary embodiment of the present disclosure;

FIG. 15 to FIG. 18 are schematic sectional views illustrating a methodof fabricating an MJT LED chip according to another exemplary embodimentof the present disclosure;

FIG. 19A, FIG. 19B, FIG. 19C and FIG. 19D show sectional views ofvarious modifications of an optical member according to the presentdisclosure;

FIG. 20A and FIG. 20B show sectional views of an optical member,illustrating an MJT LED module according to a further exemplaryembodiment of the present disclosure;

FIG. 21 is a sectional view illustrating dimensions of an MJT LED moduleused for simulation;

FIG. 22A, FIG. 22B and FIG. 22C show graphs depicting a shape of anoptical member of FIG. 21;

FIG. 23 shows traveling directions of light beams entering the opticalmember of FIG. 21;

FIG. 24A and FIG. 24B show graphs depicting illuminance distribution.Specifically, FIG. 24A is a graph depicting illuminance distribution ofan MJT LED, and FIG. 24B is a graph showing illuminance distribution ofan MJT LED module using an optical member;

FIG. 25A and FIG. 25B show graphs depicting light beam distributions.Specifically, FIG. 25A is a graph depicting a light beam distribution ofan MJT LED and FIG. 25B is a graph depicting a light beam distributionof an MJT LED module using an optical member;

FIG. 26 is a sectional view of an MJT LED module according to oneexemplary embodiment of the present disclosure;

FIG. 27A, FIG. 27B and FIG. 27C illustrate sectional views of the MJTLED module taken along lines a-a, b-b and c-c of FIG. 26, respectively;

FIG. 28 is a detailed view of an optical member of the MJT LED moduleshown in FIG. 26;

FIG. 29 shows a light beam angle distribution of the MJT LED moduleusing the optical member of FIG. 28;

FIG. 30 is a sectional view of an optical member according to anotherexemplary embodiment of the present disclosure;

FIG. 31 shows a beam angle distribution curve of an MJT LED module usingthe optical member of FIG. 30;

FIG. 32A and FIG. 32B show an optical member according to ComparativeExample 1 and a beam angle distribution curve thereof;

FIG. 33A and FIG. 33B show an optical member according to ComparativeExample 2 and a light beam angle distribution thereof;

FIG. 34 is a schematic plan view of an MJT LED chip according to oneexemplary embodiment of the present disclosure;

FIG. 35 is a schematic cross-sectional view of the MJT LED chip takenalong section B-B of FIG. 34;

FIG. 36 through FIG. 41 are schematic cross-sectional views illustratinga method of fabricating an MJT LED chip according to one exemplaryembodiment of the present disclosure;

FIG. 42 is a schematic cross-sectional view of an MJT LED chip accordingto another exemplary embodiment of the present disclosure;

FIG. 43A and FIG. 43B are schematic views comparing a backlight unit(FIG. 43A) in the related art with a backlight unit (FIG. 43B) accordingto one exemplary embodiment of the present disclosure.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

The present disclosure will be described more fully hereinafter withreference to the accompanying drawings, in which exemplary embodimentsof the disclosure are illustrated. These embodiments will be describedsuch that the disclosure can be easily understood by a person havingordinary knowledge in the art. Here, although various embodiments aredisclosed herein, it should be understood that these embodiments are notintended to be exclusive. For example, individual structures, elementsor features of a particular embodiment are not limited to thatparticular embodiment and can be applied to other embodiments withoutdeparting from the spirit and scope of the disclosure. In addition, itshould be understood that locations or arrangement of individualcomponents in each of the embodiments may be changed without departingfrom the spirit and scope of the present disclosure. Therefore, thefollowing embodiments are not to be construed as limiting thedisclosure, and the present disclosure should be limited only by theclaims and equivalents thereof. Like components will be denoted by likereference numerals, and lengths, areas, thicknesses and shapes of thecomponents are not drawn to scale throughout the accompanying drawings.

Now, exemplary embodiments of the disclosure will be described in detailwith reference to the accompanying drawings so as to be easily realizedby a person having ordinary knowledge in the art.

Exemplary Embodiment of the Present Disclosure

As used herein, the term “MJT LED chip” means a single LED chip, inwhich a plurality of light emitting cells is connected to each other viainterconnection lines. The MJT LED chip may include N light emittingcells (N is an integer of 2 or more), in which N may be set in variousways as needed. Further, each of the light emitting cells may have aforward voltage in the range from 3V to 3.6V, but is not limitedthereto. Accordingly, a forward voltage of a certain MJT LED chip (orMJT LED) is proportional to the number of light emitting cells includedin the corresponding MJT LED chip. Since the number of light emittingcells included in the MJT LED chip may be set in various ways as needed,the MJT LED chip according to the present disclosure may be configuredto have an operating voltage of 6V to 36V depending upon a specificationof an operating power generator (for example, a DC converter) used in abacklight unit, but is not limited thereto. Further, operating currentof the MJT LED chip is much smaller than a typical single-cell LED, andmay range, for example, from 20 mA to 40 mA, without being limitedthereto.

In addition, the term “MJT LED” refers to a light emitting device or anLED package, on which the MJT LED chip according to the presentdisclosure is mounted.

Further, the term “MJT LED module” refers to a component in which asingle MJT LED and a single optical member corresponding to the MJT LEDare coupled to each other. The corresponding optical member may bedirectly placed on the MJT LED, or may be placed on a printed circuitboard on which the MJT LED is mounted. Regardless of displacement of theoptical member, the case wherein a single MJT LED and a single opticalmember corresponding thereto are coupled to each other will be referredto as the MJT LED module.

Further, the term “backlight module” means a lighting module, in which aplurality of MJT LEDs is disposed on a printed circuit board and opticalmembers are provided corresponding to the respective MJT LEDs. Thus, theterm “backlight module” may mean a lighting module in which plural MJTLED modules are mounted on a printed circuit board in a predeterminedmanner. In one aspect, a backlight module according to one exemplaryembodiment of the disclosure may be a direct type backlight module.However, it should be understood that the present disclosure is notlimited thereto. In other embodiments, the backlight module according tothe present disclosure may be used as a light source for surfacelighting. Accordingly, it will be apparent to those skilled in the artthat any component including the subject matter of the backlight moduleaccording to the present disclosure falls within the scope of thepresent disclosure, despite the name of the component.

Overview of Backlight Unit Using MJT LEDs

Before detailed descriptions of the backlight unit according to thepresent disclosure are given, several technical features of the presentdisclosure will be described. The present disclosure is based oncharacteristics of an MJT LED in order to solve the aforementionedproblems in the related art. That is, in order to solve the problems dueto low voltage and high current operation characteristics of a typicalsingle-cell LED in the related art, the present disclosure has beencreated based on high voltage and low current operation characteristicsof the MJT LED (for example, an operating voltage of 6 V to 36 V and anoperating current of 20 mA to 40 mA), and provides a backlight moduleusing such an MJT LED. As described above, unlike a typical single-cellLED, the MJT LED may include any number of light emitting cells and mayhave various forward voltages depending upon the number of lightemitting cells included therein. In addition, since the MJT LED includesa plurality of light emitting cells, it is possible to illuminate awider area than the typical single-cell LED, and since the MJT LED isconstituted by a single MJT LED chip, design and application of anoptical member therefor can be easily achieved. Thus, when using such anMJT LED, one divided area among a plurality of divided areas in a liquidcrystal panel can be covered by one MJT LED module (that is, one MJT LEDand one optical member). As a result, the number of LEDs required forthe backlight module is reduced as compared with the typical single-cellLED. Consequently, according to the present disclosure, a plurality ofMJT LED modules is used to constitute a backlight module and a backlightunit is configured to allow independent control of each of the MJT LEDsconstituting the backlight module, thereby achieving the above and otherobjects of the present disclosure.

Now, referring to FIG. 2 through FIG. 4 and FIG. 43, a backlight unit1000 according to one exemplary embodiment of the disclosure will bedescribed in more detail.

First, FIG. 2 is a schematic block diagram of a backlight unit employingMJT LEDs according to one exemplary embodiment of the presentdisclosure. Referring to FIG. 2, the backlight unit 1000 according tothis embodiment includes a backlight control module 400 and a backlightmodule 300. Further, the backlight units illustrated in the presentdisclosure may further include a floodlighting plate (not shown).

More specifically, the backlight control module 400 according to thisdisclosure includes an operating power generator 410, whichgenerates/outputs DC power based on input voltage Vin input from anexternal power source, and an operation controller 420 controllingoperation of each of a plurality of MJT LEDs 100 constituting thebacklight module 300 (on/off control and dimming control). The operatingpower generator 410 generally generates stable DC voltage such as 12V,24V, 48V, and the like, as operating power and supplies the DC voltageto the plurality of MJT LEDs 100 constituting the backlight module 300.Here, the input voltage Vin supplied to the operating power generator410 may be a commercially available alternating voltage of 220V or 110V.The operating power generator 410 may have substantially the sameconfiguration as the typical operating power generator 410 as shown inFIG. 1.

The backlight module 300 according to this disclosure may include aplurality of MJT LEDs 100 and optical members (not shown in FIG. 2)corresponding to the respective MJT LEDs 100 and disposed in a regulararrangement (for example, in a matrix arrangement) on a printed circuitboard (not shown in FIG. 2).

FIG. 43B is a schematic view illustrating a configuration of thebacklight unit according to the present disclosure. Referring to FIG.43B, the printed circuit board 110 may include a plurality of blocks 110b. The block 110 b refers to a partial area of the printed circuit board110 including an area on which at least one of the plurality of MJT LEDsare mounted, upon mounting the plurality of MJT LEDs on the printedcircuit board 110. Specifically, one block 110 b may include at leastone MJT LED. In an example, one block 110 b may include only one MJTLED. However, the present disclosure is not limited thereto, but oneblock 110 b may include a plurality of MJT LEDs.

M blocks 110 b are disposed in a horizontal direction and N blocks 110 bare disposed in a vertical direction to form an M×N matrix arrangement.As shown FIG. 43B, for example, 45 blocks 110 b may constitute a 9×5matrix arrangement. A horizontal length L1 of each of the blocks 110 bmay be 60 mm or less. In addition, a vertical length L2 of each of theblocks 110 b may be 55 mm or less.

In the exemplary embodiment shown in FIG. 2, it is assumed that M MJTLEDs 100 are disposed in a longitudinal direction and N MJT LEDs 100 aredisposed in a transverse direction to form an M×N matrix arrangementwithin the backlight module 300. In this case, the respective MJT LEDsmay be disposed such that one MJT LED corresponds to one of the blocks(“one-to-one mapping configuration”). In addition, an MJT LED placed ata left side uppermost portion of the backlight module will be referredto as a 1-1st MJT LED (100_11) and an MJT LED placed at a right sidelowermost portion thereof will be referred to as an M-Nth MJT LED(100_MN).

Here, it should be noted that, unlike the related art shown in FIG. 1,the MJT LEDs 100 within the backlight module 300 according to theembodiment of FIG. 2 are independently connected to the operating powergenerator 410 and the operation controller 420 instead of beingconnected to each other in series, in parallel, or in series/parallel.That is, in the embodiment shown in FIG. 2, an anode terminal of eachMJT LED 100 is independently connected to the operating power generator410 and a cathode terminal of each MJT LED 100 is independentlyconnected to the operation controller 420. When the respective MJT LEDsand the respective blocks correspond to each other with the one-to-onemapping configuration, the blocks may be configured to be independentlyconnected to the operating power generator 410 and the operatingcontroller 420.

With this configuration, the operation controller 420 according to thisdisclosure may independently control operation of each of the pluralityof MJT LEDs 100 constituting the backlight module 300. Morespecifically, the operation controller 420 according to this disclosuremay control a dimming level of a specific MJT LED among the plurality ofMJT LEDs 100 in response to a dimming signal (Dim). When the respectiveMJT LEDs and the respective blocks correspond to each other with theone-to-one mapping configuration, the operating controller 420 mayindependently control an operation of each of the plurality of blocks.

In one embodiment, the operation controller 420 according to the presentdisclosure includes a PWM (Pulse Width Modulation) controller (notshown) and may perform dimming control through pulse width modulationcontrol with respect to operating power supplied to a specific MJT LED,which is a dimming control target, among the MJT LEDs 100. Particularly,unlike the typical backlight unit in the related art as shown in FIG. 1,the backlight unit 1000 according to the present disclosure as shown inFIG. 2 includes the plurality of MJT LEDs 100, each of which isconnected to the operating power generator 410 to independently receiveoperating power, thereby enabling dimming control in such a pulse widthmodulation manner. Specifically, the operating controller 420 maycontrol a duty ratio of operating power in the range of 0% to 100%. Forexample, when there is a need for dimming control of the 1-1st MJT LED(100_11), the operation controller 420 performs pulse width modulationof the generated operating power at a predetermined duty ratio (forexample, 60%) in response to a dimming signal (Dim), and supplies themodified operating power to the 1-1st MJT LED (100_11) to performdimming control of the 1-1st MJT LED (100_11). At this time, operatingpower, which is not subjected to pulse width modulation and has a dutyratio of 100%, will be supplied to other MJT LEDs except for the 1-1stMJT LED (100_11). Alternatively, operating power, which is subjected topulse width modulation at a normal duty ratio (a duty ratio of, forexample, 80% when no separate dimming control is provided), is providedto the other MJT LEDs except for the 1-1st MJT LED (100_11).Consequently, the backlight unit 1000 according to the presentdisclosure allows local dimming with respect to only the 1-1st MJT LED(100_11). Of course, it will be apparent to those skilled in the artthat it is possible to perform simultaneous dimming control with respectto the plurality of MJT LEDs at the same dimming level and/or atdifferent dimming levels for the respective MJT LEDs through PWMcontrol. The operating power described above may be a DC operatingvoltage. The PWM controller for PWM control of the operating power iswell known in the art, and thus, a detailed description thereof will beomitted.

In another embodiment, the operation controller 420 according to thepresent disclosure includes an operating current detector (not shown)and an operating current controller (not shown), and may perform dimmingcontrol by controlling the operating current supplied to a specific MJTLED, which is a dimming control target, among the MJT LEDs 100.Particularly, unlike the typical backlight unit shown in FIG. 1, in thebacklight unit 1000 according to the present disclosure shown in FIG. 2,each of the plural MJT LEDs 100 is independently connected to theoperation controller 420, thereby enabling dimming control by control ofthe operating current of each of the MJT LEDs. Here, the operatingcurrent detector and the operating current controller included in theoperation controller 420 correspond one to one to each of the MJT LEDs100. Accordingly, when the backlight module 300 is composed of M×N MJTLEDs 100 as described above, the operation controller 420 includes M×Noperating current detectors and M×N operating current controllers. Forexample, when there is a need for dimming control with respect to anM-Nth MJT LED (100_MN), the operation controller 420 detects operatingcurrent flowing through the M-Nth MJT LED (100_MN) using the operatingcurrent detector, and changes the operating current flowing through theM-Nth MJT LED (100_MN) (for example, to 100% of a maximum operatingcurrent) in response to a dimming signal (Dim), thereby performingdimming control with respect to the M-Nth MJT LED (100_MN). For example,the operating controller 420 may control the operation current in therange of 0% to 100%. Here, since normal operating current (a presetstandard operating current, for example, 80% of the maximum operatingcurrent, when there is no separate dimming control) flows through otherMJT LEDs except for the M-Nth MJT LED (100_MN), local dimming can beperformed with respect only to the M-Nth MJT LED (100_MN). It will beapparent to those skilled in the art that dimming control of theplurality of MJT LEDs can be performed to the same dimming level throughsimultaneous control of the operating current with respect to theplurality of MJT LEDs and/or to different dimming levels for therespective MJT LEDs. In such an embodiment, since there is no need forindependent supply of operating power to the MJT LEDs 100, the anodeterminal of each of the MJT LEDs 100 may be connected in parallel to oneoperating power line connected to the operating power generator 410,unlike the embodiment shown in FIG. 2. The operating current detectorand the operating current controller are well known in the art anddetailed descriptions thereof will thus be omitted.

The operating controller 420 according to the present disclosure mayinclude a plurality of switch controllers (not shown). The switchcontrollers may be each disposed between the plurality of MJT LEDs.Specifically, the switch controllers may be disposed between one MJT LEDand an adjacent MJT LED. More specifically, the switch controllers maybe disposed between one MJT LED and the remaining MJT LEDs. That is, theswitch controllers may be disposed between one MJT LED of M×N MJT LEDsand the remaining M×N-1 MJT LEDs, which may correspond to all MJT LEDincluded in the backlight module 300 as well as one MJT LED.

The respective switch controllers may electrically connect two MJT LEDsconnected by the switch controller, and may also electrically insulatethe two MJT LEDs according to a switching operation. Thus, a pluralityof MJT LEDs may be connected to each other in series and/or in parallelthrough the switch controllers. Consequently, a desired structure of thebacklight module 300 may be easily implemented.

The backlight unit according to the present disclosure may furtherinclude a floodlighting plate (not shown). The floodlighting plate maybe disposed over the backlight module 300. Specifically, thefloodlighting plate may be disposed over the printed circuit board 110of the backlight module 300. The floodlighting plate may serve todiffuse light emitted from the MJT LEDs of the backlight module 300. Adistance between a lower surface of the floodlighting plate and an uppersurface of the printed circuit board may be 18 mm or more.

Overview of MJT LED and MJT LED Module

FIG. 3 is a schematic sectional view of an MJT LED module according toone exemplary embodiment of the present disclosure, and FIG. 4 is aschematic perspective view of the MJT LED according to the one exemplaryembodiment of the present disclosure. Now, detailed configurations of anMJT LED 100 and an MJT LED module according to embodiments of thepresent disclosure will be described with reference to FIG. 3 and FIG.4.

Referring to FIG. 3, the MJT LED module includes an MJT LED 100 and anoptical member 130. When the MJT LED 100 is mounted on a printed circuitboard 110, the corresponding optical member 130 is mounted on theprinted circuit board 110 at a place corresponding to the position ofthe MJT LED 100. For example, each block of the printed circuit board110 may include one optical member. As described above, in otherembodiments, the optical member 130 may be directly connected to the MJTLED 100. More specifically, the optical member 130 may be formed bymolding a resin on the MJT LED. Although the printed circuit board 110is partially shown in FIG. 3, a plurality of MJT LEDs 100 and theoptical members 130 corresponding thereto are disposed on a singleprinted circuit board 110 in various arrangements such as a matrixarrangement or a honeycomb arrangement to form the backlight module 300as described above.

The printed circuit board 110 is formed on an upper surface thereof withconductive land patterns to which terminals of the MJT LED 100 arebonded. Further, the printed circuit board 110 may include a reflectivelayer on the upper surface thereof. The printed circuit board 110 may bea MCPCB (Metal-Core PCB) based on a metal having good thermalconductivity. Alternatively, the printed circuit board 110 may be formedof an insulating substrate material such as FR4. Although not shown, theprinted circuit board 110 may be provided at a lower side thereof with aheat sink to dissipate heat from the MJT LED 100.

As clearly shown in FIG. 4, the MJT LED 100 may include a housing 121,an MJT LED chip 123 mounted on the housing 121, and a wavelengthconversion layer 125 covering the MJT LED chip 123. The MJT LED 100further includes lead terminals (not shown) supported by the housing121.

The housing 121 forms a package body and may be formed by injectionmolding of a plastic resin such as PA, PPA, and the like. In this case,the housing 121 may be formed in a state of supporting the leadterminals by an injection molding process, and may have a cavity 121 afor mounting the MJT LED chip 123 therein. The cavity 121 a defines alight exit area of the MJT LED 100.

The lead terminals are separated from each other within the housing 121and extend outside of the housing 121 to be bonded to the land patternson the printed circuit board 110.

The MJT LED chip 123 is mounted on the bottom of the cavity 121 a andelectrically connected to the lead terminals. The MJT LED chip 123 maybe a gallium nitride-based MJT LED which emits UV light or blue light. Adetailed configuration of the MJT LED chip 123 according to the presentdisclosure and a method of manufacturing the same will be describedbelow with reference to FIG. 5 to FIG. 18.

The wavelength conversion layer 125 covers the MJT LED chip 123. In oneembodiment, the wavelength conversion layer 125 may be formed by fillingthe cavity 121 a with a molding resin containing phosphors aftermounting the MJT LED chip 123 in the cavity 121 a. At this time, thewavelength conversion layer 125 may fill the cavity 121 a of the housing121 and have a substantially flat or convex upper surface. Further, amolding resin having a shape of the optical member may be formed on thewavelength conversion layer 125.

In another embodiment, the MJT LED chip 123, which has a coating layerof the phosphors formed by conformal coating, may be mounted on thehousing 121. Specifically, the coating layer of the phosphors may beformed on the MJT LED chip 123 by conformal coating and the MJT LED chip123 having the conformal coating layer may be mounted on the housing121. The MJT LED chip 123 having the conformal coating layer may bemolded with a transparent resin. In addition, the molding resin may havethe shape of the optical member and thus may act as a primary opticalmember.

The wavelength conversion layer 125 converts-wavelengths of lightemitted from the MJT LED chip 123 to provide light of mixed colors, forexample, white light.

The wavelength conversion layer 125 may include KSF-based and/orUCD-based phosphors. Thus, light emitted from the MJT LED chip 123 topenetrate through the wavelength conversion layer 125 may have an NTSCcolor reproduction ratio of 70% or more.

The MJT LED 100 is designed to have a light beam distribution of amirror symmetry structure, particularly, a light beam distribution of arotational symmetry structure. At this time, an axis of the MJT LEDdirected towards the center of the light beam distribution is defined asan optical axis L. That is, the MJT LED 100 is designed to have a lightbeam distribution which is bilaterally symmetrical with respect to theoptical axis L. Generally, the cavity 121 a of the housing 121 may havea mirror symmetry structure, and the optical axis L may be defined as astraight line passing through the center of the cavity 121 a.

The optical member 130 includes a light incident face through whichlight emitted from the MJT LED 100 enters the optical member and a lightexit face through which the light exits the optical member at a widerlight beam distribution than that of the MJT LED 100, thereby enablinguniform distribution of the light emitted from MJT LED 100. The opticalmember 130 according to the present disclosure will be described belowwith reference to FIG. 19A to FIG. 33B.

Configuration of MJT LED Chip and Method of Manufacturing the Same

Next, the configuration of the MJT LED chip 123 mounted on the MJT LEDaccording to the present disclosure and a method of manufacturing thesame will be described in more detail with reference to FIG. 5 to FIG.18.

FIG. 5 is a schematic plan view of an MJT LED chip according to oneexemplary embodiment of the present disclosure, and FIG. 6 is aschematic sectional view of the MJT LED chip taken along line B-B ofFIG. 5.

Referring to FIG. 5 and FIG. 6, the MJT LED chip 123 includes a growthsubstrate 51, light emitting cells S1, S2, a transparent electrode layer61, a current blocking layer 60 a, an insulation layer 60 b, aninsulation protective layer 63, and an interconnection line 65. Further,the MJT LED chip 123 may include a buffer layer 53.

The growth substrate 51 may be an insulation or conductive substrate,and may include, for example, a sapphire substrate, a gallium nitridesubstrate, a silicon carbide (SiC) substrate, or a silicon substrate. Inaddition, the growth substrate 51 may have a convex-concave pattern (notshown) on an upper surface thereof as in a patterned sapphire substrate.

A first light emitting cell S1 and a second light emitting cell S2 areseparated from each other on a single growth substrate 51. Each of thefirst and second light emitting cells S1, S2 has a stack structure 56,which includes a lower semiconductor layer 55, an upper semiconductorlayer 59 placed on a region of the lower semiconductor layer, and anactive layer 57 interposed between the lower semiconductor layer and theupper semiconductor layer. Here, the upper and lower semiconductorlayers may be an n-type semiconductor layer and a p-type semiconductorlayer, respectively, or vice versa.

Each of the lower semiconductor layer 55, the active layer 57 and theupper semiconductor layer 59 may be formed of a gallium nitride-basedsemiconductor material, that is, (Al, In, Ga)N. The compositionalelements and ratio of the active layer 57 are determined depending upondesired wavelengths of light, for example, UV light or blue light, andthe lower semiconductor layer 55 and the upper semiconductor layer 59are formed of a material having a greater band gap than the active layer57.

The lower semiconductor layer 55 and/or the upper semiconductor layer 59may have a single layer structure, as shown in FIG. 5. Alternatively,these semiconductor layers may have a multilayer structure. Further, theactive layer 57 may have a single quantum-well structure or amulti-quantum well structure.

MN Each of the first and second light emitting cells S1, S2 may have aslanted side surface, an inclination of which may range, for example,from 15° to 80° relative to an upper surface of the growth substrate 51.

The active layer 57 and the upper semiconductor layer 59 are placed onthe lower semiconductor layer 55. An upper surface of the lowersemiconductor layer 55 may be completely covered by the active layer 57such that only a side surface thereof is exposed.

Although portions of the first light emitting cell S1 and the secondlight emitting cell S2 are shown in FIG. 6, the first and second lightemitting cells S1, S2 may have a similar or the same structure as thatshown in FIG. 5. That is, the first light emitting cell S1 and thesecond light emitting cell S2 may have the same gallium nitride-basedsemiconductor stack structure, and may have slanted side surfaces of thesame structure.

The buffer layer 53 may be interposed between the light emitting cellsS1, S2 and the growth substrate 51. The buffer layer 53 relieves latticemismatch between the growth substrate 51 and the lower semiconductorlayer 55 formed thereon.

The transparent electrode layer 61 is placed on each of the lightemitting cells S1, S2. That is, a first transparent electrode layer 61is placed on the first light emitting cell S1 and a second transparentelectrode layer 61 is placed on the second light emitting cell S2. Thetransparent electrode layer 61 may be placed on the upper semiconductorlayer 59 to be connected to the upper semiconductor layer 59, and mayhave a narrower area than the upper semiconductor layer 59. That is, thetransparent electrode layer 61 may be recessed from an edge of the uppersemiconductor layer 59. With this structure, it is possible to preventcurrent crowding at the edge of the transparent electrode layer 61through the side surfaces of the light emitting cells S1, S2.

In another aspect, the current blocking layer 60 a may be placed on eachof the light emitting cells S1, S2. That is, the current blocking layer60 a is placed between the transparent electrode layer 61 and each ofthe light emitting cells S1, S2. Part of the transparent electrode layer61 is placed on the current blocking layer 60 a. The current blockinglayer 60 a may be placed near an edge of each of the light emittingcells S1, S2, but is not limited thereto. Alternatively, the currentblocking layer 60 a may be placed in a central region of each of thelight emitting cells S1, S2. The current blocking layer 60 a is formedof an insulation material and, particularly, may include a distributedBragg reflector in which layers having different indices of refractionare alternately stacked one above another.

The insulation layer 60 b covers a portion of the side surface of thefirst light emitting cell S1. As shown in FIG. 5 and FIG. 6, theinsulation layer 60 b may extend to a region between the first lightemitting cell S1 and the second light emitting cell S2, and may cover aportion of a side surface of the lower semiconductor layer 55 of thesecond light emitting cell S2. The insulation layer 60 b may have thesame structure and the same material as those of the current blockinglayer 60 a, and may include a distributed Bragg reflector, without beinglimited thereto. The insulation layer 60 b may be formed of a differentmaterial than that of the current blocking layer 60 a by a differentprocess. Here, when the insulation layer 60 b is a distributed Braggreflector formed by stacking multiple layers, it is possible toefficiently suppress generation of defects such as pinholes in theinsulation layer 60 b. The insulation layer 60 b may be connected to thecurrent blocking layer 60 a to form continuous layers, but is notlimited thereto. In other embodiments, the insulation layer 60 b may beseparated from the current blocking layer 60 a.

The interconnection line 65 electrically connects the first lightemitting cell S1 to the second light emitting cell S2. Theinterconnection line 65 includes a first connection section 65 p and asecond connection section 65 n. The first connection section 65 p iselectrically connected to the transparent electrode layer 61 on thefirst light emitting cell S1, and the second connection section 65 n iselectrically connected to the lower semiconductor layer 55 of the secondlight emitting cell S2. The first connection section 65 p may be placednear one edge of the first light emitting cell S1, but is not limitedthereto. In other embodiments, the first connection section 65 p may beplaced in the central region of the first light emitting cell S1.

The second connection section 65 n may contact the slanted side surfaceof the second light emitting cell S2, particularly, the slanted sidesurface of the lower semiconductor layer 55 of the second light emittingcell S2. Further, as shown in FIG. 5, the second connection section 65 nmay electrically contact the slanted side surface of the lowersemiconductor layer 55 while extending to both sides along thecircumference of the second light emitting cell S2. The first lightemitting cell S1 is connected to the second light emitting cell S2 inseries by the first and second connection sections 65 p, 65 n of theinterconnection line 65.

The interconnection line 65 may contact the transparent electrode layer61 over an overlapping region with the transparent electrode layer 61.In the related art, a portion of the insulation layer is placed betweenthe transparent electrode layer and the interconnection line. On thecontrary, according to the present disclosure, the interconnection line65 may directly contact the transparent electrode layer 61 without anyinsulation material interposed therebetween.

Further, the current blocking layer 60 a may be placed over theoverlapping region between the interconnection line 65 and thetransparent electrode layer 61, and the current blocking layer 60 a andthe insulation layer 60 b may be placed over an overlapping regionbetween the interconnection line 65 and the first light emitting cellS1. Further, the insulation layer 60 b may be placed between the secondlight emitting cell S2 and the interconnection line 65 in other regionsexcluding a connection region between the interconnection line 65 andthe second light emitting cell S2.

In FIG. 5, the first connection section 65 p and the second connectionsection 65 n of the interconnection line 65 are connected to each otherthrough two paths. However, it should be understood that the first andsecond connection sections may be connected to each other via a singlepath.

When the current blocking layer 60 a and the insulation layer 60 b havereflective characteristics like the distributed Bragg reflector, thecurrent blocking layer 60 a and the insulation layer 60 b are preferablyplaced substantially in the same region as the region for theinterconnection line 65 within a region having an area of two times orless the area of the interconnection line 65. The current blocking layer60 a and the insulation layer 60 b block light emitted from the activelayer 57 from being absorbed into the interconnection line 65. However,when occupying an excessively large area, the current blocking layer 60a and the insulation layer 60 b can block emission of light to theoutside. Thus, there is a need for restriction of the area thereof.

The insulation protective layer 63 may be placed outside the region ofthe interconnection line 65. The insulation protective layer 63 coversthe first and second light emitting cells S1, S2 outside the region ofthe interconnection line 65. The insulation protective layer 63 may beformed of silicon oxide (SiO₂) or silicon nitride. The insulationprotective layer 63 has an opening through which the transparentelectrode layer 61 on the first light emitting cell S1 and the lowersemiconductor layer of the second light emitting cell S2 are exposed,and the interconnection line 65 may be placed within the opening.

A side surface of the insulation protective layer 63 and a side surfaceof the interconnection line 65 may face each other, and may contact eachother. Alternatively, the side surface of the insulation protectivelayer 63 and the side surface of the interconnection line 65 may beseparated from each other while facing each other.

According to the present embodiment, since the second connection section65 n of the interconnection line 65 electrically contacts the slantedside surface of the second light emitting cell S2, there is no need toexpose the upper surface of the lower semiconductor layer 55 of thesecond light emitting cell S2. Accordingly, there is no need for partialremoval of the second semiconductor layer 59 and the active layer 57,thereby increasing an effective light emitting area of the MJT LED chip123.

In addition, the current blocking layer 60 a and the insulation layer 60b may be formed of the same material and have the same structure, andthus may be formed at the same time by the same process. Further, sincethe interconnection line 65 is placed within the opening of theinsulation protective layer 63, the insulation protective layer 63 andthe interconnection line 65 may be formed using the same mask pattern.

Although two light emitting cells including the first light emittingcell S1 and the second light emitting cell S2 are illustrated in thisembodiment, it should be understood that the present disclosure is notlimited thereto. That is, a greater number of light emitting cells maybe electrically connected to each other via the interconnection lines65. For example, the interconnection lines 65 may electrically connectthe lower semiconductor layers 55 and the transparent electrode layers61 of adjacent light emitting cells to each other to form a series arrayof light emitting cells. A plurality of such arrays may be formed andconnected in inverse-parallel to each other to be operated by an ACpower source connected thereto. In addition, a bridge rectifier (notshown) may be connected to the series array of light emitting cells toallow the light emitting cells to be operated by the AC power source.The bridge rectifier may be formed by bridging the light emitting cellshaving the same structure as that of the light emitting cells S1, S2using the interconnection lines 65.

FIG. 7 to FIG. 13 are schematic sectional views illustrating a method offabricating an MJT LED chip according to one exemplary embodiment of thepresent disclosure.

Referring to FIG. 7, a semiconductor stack structure 56 including alower semiconductor layer 55, an active layer 57 and an uppersemiconductor layer 59 is formed on a growth substrate 51. In addition,a buffer layer 53 may be formed on the growth substrate 51 beforeformation of the lower semiconductor layer 55.

The growth substrate 51 may be formed of a material selected from amongsapphire (Al₂O₃), silicon carbide (SiC), zinc oxide (ZnO), silicon (Si),gallium arsenic (GaAs), gallium phosphide (GaP), lithium alumina(LiAl₂O₃), boron nitride (BN), aluminum nitride (AlN), and galliumnitride (GaN), without being limited thereto. That is, the material forthe growth substrate 51 may be selected in various ways depending uponmaterials of semiconductor layers to be formed on the growth substrate51. Further, the growth substrate 51 may have a convex-concave patternon an upper surface thereof as in a patterned sapphire substrate.

The buffer layer 53 is formed to relieve lattice mismatch between thegrowth substrate 51 and the semiconductor layer 55 formed thereon, andmay be formed of, for example, gallium nitride (GaN) or aluminum nitride(AlN). When the growth substrate 51 is a conductive substrate, thebuffer layer 53 is preferably formed of an insulation layer or asemi-insulating layer. For example, the buffer layer 53 may be formed ofAlN or semi-insulating GaN.

Each of the lower semiconductor layer 55, the active layer 57 and theupper semiconductor layer 59 may be formed of a gallium nitride-basedsemiconductor material, for example, (Al, In, Ga)N. The lower and uppersemiconductor layers 55, 59 and the active layer 57 may beintermittently or continuously formed by metal organic chemical vapordeposition (MOCVD), molecular beam epitaxy, hydride vapor phase epitaxy(HVPE), and the like.

Here, the lower and upper semiconductor layers may be n-type and p-typesemiconductor layers, or vice versa. Among the gallium nitride-basedcompound semiconductor layers, an n-type semiconductor layer may beformed by doping an n-type impurity, for example, silicon (Si), and ap-type semiconductor layer may be formed by doping a p-type impurity,for example, magnesium (Mg).

Referring to FIG. 8, a plurality of light emitting cells S1, S2separated from each other is formed by a photolithography and etchingprocess. Each of the light emitting cells S1, S2 is formed to have aslanted side surface. In a typical method of manufacturing an MJT LEDchip, an additional photolithography and etching process is performed topartially expose an upper surface of the lower semiconductor layer 55 ofeach of the light emitting cells S1, S2. However, in this embodiment,the photolithography and etching process performed to partially exposethe upper surface of the lower semiconductor layer 55 is omitted.

Referring to FIG. 9, a current blocking layer 60 a covering some regionon the first light emitting cell S1 and an insulation layer 60 bpartially covering the side surface of the first light emitting cell S1are formed. The insulation layer 60 b may extend to cover a regionbetween the first light emitting cell S1 and the second light emittingcell S2 while partially covering a side surface of the lowersemiconductor layer 55 of the second light emitting cell S2.

The current blocking layer 60 a and the insulation layer 60 b may beformed by depositing an insulation material layer, followed bypatterning through photolithography and etching. Alternatively, thecurrent blocking layer 60 a and the insulation layer 60 b may be formedof an insulation material layer by a lift-off technique. Particularly,each of the current blocking layer 60 a and the insulation layer 60 bmay be a distributed Bragg reflector formed by alternately stackinglayers having different indices of refraction, for example, SiO₂ andTiO₂ layers. When the insulation layer 60 b is a distributed Braggreflector formed by stacking multiple layers, it is possible toefficiently suppress generation of defects such as pinholes in theinsulation layer 60 b, whereby the insulation layer 60 b can be formedto a smaller thickness than in the related art.

As shown in FIG. 9, the current blocking layer 60 a and the insulationlayer 60 b may be connected to each other. However, it should beunderstood that the present disclosure is not limited thereto.

Then, a transparent electrode layer 61 is formed on the first and secondlight emitting cells S1, S2. The transparent electrode layer 61 may beformed of an indium tin oxide (ITO) layer, a conductive oxide layer suchas a zinc oxide layer, or a metal layer such as Ni/Au. The transparentelectrode layer 61 is connected to the upper semiconductor layer 59 andis partially placed on the current blocking layer 60 a. The transparentelectrode layer 61 may be formed by a lift-off process, without beinglimited thereto. Alternatively, the transparent electrode layer 61 maybe formed by a photolithography and etching process.

Referring to FIG. 10, an insulation protective layer 63 is formed tocover the first and second light emitting cells S1, S2. The insulationprotective layer 63 covers the transparent electrode layer 61 and theinsulation layer 60 b. In addition, the insulation protective layer 63may cover an overall area of the first and second light emitting cellsS1, S2. The insulation protective layer 63 may be formed of aninsulation material layer, such as a silicon oxide or silicon nitridelayer, by chemical vapor deposition.

Referring to FIG. 11, a mask pattern 70 having an opening is formed onthe insulation protective layer 63. The opening of the mask pattern 70corresponds to a region for an interconnection line. Then, some regionof the insulation protective layer 63 is removed by etching through themask pattern 70. As a result, an opening is formed on the insulationprotective layer 63 to expose some of the transparent electrode layer 61and the insulation layer 60 b while exposing the slanted side surface ofthe lower semiconductor layer 55 of the second light emitting cell S2.

Referring to FIG. 12, with the mask pattern 70 remaining on theinsulation protective layer 63, a conductive material is deposited toform the interconnection line 65 within the opening of the mask pattern70. Here, some of the conductive material 65 a may be deposited on themask pattern 70. The conductive material may be deposited by plating,e-beam evaporation, sputtering, and the like.

Referring to FIG. 11, the mask pattern 70, together with some of theconductive material 65 a, is removed from the mask pattern 70. As aresult, the interconnection line 65 electrically connecting the firstand second light emitting cells S1, S2 to each other is completed.

Here, a first connection section 65 p of the interconnection line 65 isconnected to the transparent electrode layer 61 of the first lightemitting cell S1, and a second connection section 65 n thereof isconnected to the slanted side surface of the lower semiconductor layer55 of the second light emitting cell S2. The first connection section 65p of the interconnection line 65 may be connected to the transparentelectrode layer 60 a within an upper region of the current blockinglayer 60 a. The interconnection line 65 is separated from the sidesurface of the first light emitting cell S1 by the insulation layer 60b.

In this embodiment, the current blocking layer 60 a and the insulationlayer 60 b are formed by the same process. As a result, the insulationprotective layer 63 and the interconnection line 65 may be formed usingthe same mask pattern 70, whereby the MJT LED chip can be manufacturedby the same number of exposure processes while adding the currentblocking layer 60 a.

FIG. 14 is a schematic sectional view of an MJT LED chip according toanother exemplary embodiment of the present disclosure.

Referring to FIG. 14, the MJT LED chip according to this embodiment isgenerally similar to the MJT LED chip described with reference to FIGS.5 and 6, and further includes a transparent conductive layer 62.

The growth substrate 51, the light emitting cells S1, S2, the bufferlayer 53, the transparent electrode layer 61, the current blocking layer60 a, the insulation layer 60 b, the insulation protective layer 63 andthe interconnection line 65 are similar to those of the light emittingdiode described with reference to FIGS. 5 and 6, and thus detaileddescriptions thereof will be omitted.

The transparent conductive layer 62 is placed between the insulationlayer 60 b and the interconnection line 65. The transparent conductivelayer 62 has a narrower width than the insulation layer 60 b, therebypreventing a short circuit of the upper semiconductor layer 59 and thelower semiconductor layer 55 due to the transparent conductive layer 62.

On the other hand, the transparent conductive layer 62 is connected to afirst transparent electrode layer 61, and may electrically connect thefirst transparent electrode layer 61 to the second light emitting cellS2. For example, the transparent conductive layer 62 may be connected atone end thereof to the lower semiconductor layer 55 of the second lightemitting cell. In addition, when two or more light emitting cells areconnected thereto, a second transparent conductive layer 62 may extendfrom a second transparent electrode layer 61 on the second lightemitting cell S2.

In this embodiment, since the transparent conductive layer 62 is placedbetween the interconnection line 65 and the insulation layer 60 b,current can flow through the transparent conductive layer 62 even in thecase where the interconnection line 65 is disconnected, therebyimproving electric stability of the MJT LED chip.

FIG. 15 to FIG. 18 are schematic sectional views illustrating a methodof fabricating an MJT LED chip according to another exemplary embodimentof the present disclosure.

Referring to FIG. 15, first, as described with reference to FIGS. 7 and8, a semiconductor stack structure 56 is formed on a growth substrate51, and a plurality of light emitting cells S1, S2 separated from eachother is formed by a photolithography and etching process. Then, asdescribed with reference to FIG. 9, a current blocking layer 60 acovering a region on the first light emitting cell S1 and an insulationlayer 60 b partially covering a side surface of the first light emittingcell S1 are formed.

As described with reference to FIG. 9, each of the current blockinglayer 60 a and the insulation layer 60 b may include a distributed Braggreflector formed by alternately stacking layers having different indicesof refraction, for example, SiO₂ and TiO₂ layers. When the insulationlayer 60 b include the distributed Bragg reflector formed by stackingmultiple layers, it is possible to efficiently suppress generation ofdefects such as pinholes in the insulation layer 60 b, whereby theinsulation layer 60 b can be formed to a smaller thickness than in therelated art.

Then, a transparent electrode layer 61 is formed on the first and secondlight emitting cells S1, S2. As described with reference to FIG. 9, thetransparent electrode layer 61 may be formed of an indium tin oxide(ITO) layer, a conductive oxide layer such as a zinc oxide layer, or ametal layer such as Ni/Au. The transparent electrode layer 61 isconnected to the upper semiconductor layer 59 and is partially placed onthe current blocking layer 60 a. The transparent electrode layer 61 maybe formed by a lift-off process, without being limited thereto.Alternatively, the transparent electrode layer 61 may be formed by aphotolithography and etching process.

During formation of the transparent electrode layer 61, a transparentconductive layer 62 is formed. The transparent conductive layer 62 maybe formed together with the transparent electrode layer 61 using thesame material and the same process. The transparent conductive layer 62is formed on the insulation layer 60 b and may be connected to thetransparent electrode layer 61. Further, the transparent conductivelayer 62 may be electrically connected at one end thereof to the slantedside surface of the lower semiconductor layer 55 of the second lightemitting cell S2.

Referring to FIG. 16, an insulation protective layer 63 is formed tocover the first and second light emitting cells S1, S2. The insulationprotective layer 63 covers the transparent electrode layer 61, thetransparent conductive layer 62, and the insulation layer 60 b. Inaddition, the insulation protective layer 63 may cover an overall areaof the first and second light emitting cells S1, S2. The insulationprotective layer 63 may be formed of an insulation material layer, suchas silicon oxide or silicon nitride, by chemical vapor deposition.

Referring to FIG. 17, as described with reference to FIG. 11, a maskpattern 70 having an opening is formed on the insulation protectivelayer 63. The opening of the mask pattern 70 corresponds to a region foran interconnection line. Then, a portion of the insulation protectivelayer 63 is removed by etching through the mask pattern 70. As a result,an opening is formed on the insulation protective layer 63 to exposesome of the transparent electrode layer 61 and the transparentconductive layer 62, while exposing the slanted side surface of thelower semiconductor layer 55 of the second light emitting cell S2.Further, the insulation layer 60 b is partially exposed through theopening.

Referring to FIG. 18, as described with reference to FIG. 12, with themask pattern 70 remaining on the insulation protective layer 63, aconductive material is deposited to form an interconnection line 65within the opening of the mask pattern 70.

Then, referring to FIG. 13, the mask pattern 70, together with some ofthe conductive material 65 a, is removed from the mask pattern 70. As aresult, the interconnection line 65 electrically connecting the firstand second light emitting cells S1, S2 to each other is completed.

In the embodiments described with reference to FIG. 7 to FIG. 13, theinsulation layer 60 b can be damaged during etching of the insulationprotective layer 63. For example, when the insulation protective layer63 is subjected to etching using an etchant, which contains, forexample, hydrofluoric acid, the insulation layer 60 b including an oxidelayer can be damaged by the etchant. In this case, the insulation layer60 b can fail to insulate the interconnection line 65 from the firstlight emitting cell S1, thereby causing a short circuit.

However, in the present embodiment, since the transparent conductivelayer 62 is placed on the insulation layer 60 b, the insulation layer 60b under the transparent conductive layer 62 can be protected frometching damage. As a result, it is possible to prevent a short circuitdue to the interconnection line 65.

In this embodiment, the transparent electrode layer 61 and thetransparent conductive layer 62 may be formed by the same process.Accordingly, the MJT LED chip can be manufactured by the same number ofexposing processes while adding the transparent conductive layer 62.

FIG. 34 is a schematic sectional view of an MJT LED chip according toanother exemplary embodiment of the present disclosure, and FIG. 35 is across-sectional view of the MJT LED chip taken along section B-B of FIG.34.

Referring to FIG. 34 and FIG. 35, the MJT LED chip 123 includes a growthsubstrate 51, light emitting cells S1, S2, transparent electrode layers61, 62, an insulation layer 60 b, an insulation protective layer 63, andan interconnection line 65. Further, the MJT LED chip 123 may include abuffer layer 53. Further, the MJT LED chip 123 may include a currentblocking layer 60 a.

The growth substrate 51 may be an insulation or conductive substrate,and may be, for example, a sapphire substrate, a gallium nitridesubstrate, a silicon carbide (SiC) substrate, or a silicon substrate. Inaddition, the growth substrate 51 may have a convex-concave pattern (notshown) on an upper surface thereof as in a patterned sapphire substrate.The convex-concave pattern may serve to effectively reflect light towardthe growth substrate among lights emitted from the light emitting cellsto improve light extraction efficiency.

A first light emitting cell S1 and a second light emitting cell S2 aredisposed on a single growth substrate 51 to be spaced apart from eachother. Each of the first and second light emitting cells S1, S2 has astack structure 56, which includes a lower semiconductor layer 55, anupper semiconductor layer 59 disposed on a region of the lowersemiconductor layer 55, and an active layer 57 interposed between thelower semiconductor layer 55 and the upper semiconductor layer 59. Here,the upper and lower semiconductor layers may be an n-type semiconductorlayer and a p-type semiconductor layer, respectively, or vice versa.

Each of the lower semiconductor layer 55, the active layer 57 and theupper semiconductor layer 59 may be formed of a gallium nitride-basedsemiconductor material, that is, (Al, In, Ga)N. The compositionalelements and ratio of the active layer 57 are determined depending upondesired wavelengths of light, for example, UV light or blue light, andthe lower semiconductor layer 55 and the upper semiconductor layer 59are formed of a material having a greater band gap than the active layer57.

The lower semiconductor layer 55 and/or the upper semiconductor layer 59may have a single layer structure, as illustrated. Alternatively, thesesemiconductor layers may have a multilayer structure. Further, theactive layer 57 may have a single quantum-well structure or amulti-quantum well structure.

Each of the first and second light emitting cells S1, S2 may have aslanted side surface having an inclination of which may range, forexample, from 15° to 80° relative to an upper surface of the growthsubstrate 51.

The active layer 57 and the upper semiconductor layer 59 are disposed onthe lower semiconductor layer 55. At least a portion of an upper surfaceof the lower semiconductor layer 55 may be covered by the active layer57, and the remaining portions thereof may not be covered by the activelayer 57, but be exposed. For example, as shown in FIG. 6 and FIG. 35,the upper surface of the lower semiconductor layer 55 may include anexposed region R. The exposed region R is a region, which is not coveredby the active layer 57 and the upper semiconductor layer 59, but inwhich a portion of the lower semiconductor layer 55, specifically, theupper surface of the lower semiconductor layer 55 is exposed. Theexposed region R may be disposed to be in parallel to a side surfacewhich is directed to an adjacent light emitting cell, among sidesurfaces of the lower semiconductor layer 55. However, the position ofthe exposed region R is not limited thereto, but may also be disposed tosurround at least a portion of the active layer 57 and the uppersemiconductor layer 59.

Although portions of the first light emitting cell S1 and the secondlight emitting cell S2 are shown in FIG. 35, the first and second lightemitting cells S1, S2 may have a similar or the same structure as thefirst and second light emitting cells S1, S2 shown in FIG. 34. That is,the first light emitting cell S1 and the second light emitting cell S2may have the same gallium nitride-based semiconductor stack structure,and may have slanted side surfaces of the same structure.

The buffer layer 53 may be interposed between the light emitting cellsS1, S2 and the growth substrate 51. The buffer layer 53 is adopted toalleviate lattice mismatch between the growth substrate 51 and the lowersemiconductor layer 55 formed thereon.

The transparent electrode layers 61, 62 are disposed on each of thelight emitting cells S1, S2. More specifically, a first transparentelectrode layer 61 is disposed on the first light emitting cell S1 and asecond transparent electrode layer 62 is disposed on the second lightemitting cell S2. The transparent electrode layers 61, 62 may bedisposed on the upper surface of the upper semiconductor layer 59 to beconnected to the upper semiconductor layer 59, and may have a narrowerarea than the upper semiconductor layer 59. That is, the transparentelectrode layers 61, 62 may be recessed from an edge of the uppersemiconductor layer 59. With this structure, it is possible to preventor reduce current crowding at the edges of the transparent electrodelayers 61, 62 through the side surfaces of the light emitting cells S1,S2.

A portion of the first transparent electrode layer 61 may be connectedto the second light emitting cell S2. Specifically, the portion of thefirst transparent electrode layer 61 may be disposed on the first lightemitting cell S1, between the first light emitting cell S1 and thesecond light emitting cell S2, and on the side surface of the lowersemiconductor layer 55 of the second light emitting cell S2. Thus, alsoin the case in which the interconnection line 65 is short-circuited, thecurrent may flow through the first transparent electrode layer 61,thereby improving electrical stability of the MJT LED chip. Further, thefirst transparent electrode layer 61 may be further extended to bedisposed on the exposed region R of the upper surface of the lowersemiconductor layer 55. The first transparent electrode layer 61 may bespaced apart from the active layer 57 and the upper semiconductor layer59 of the second light emitting cell S2.

The insulation layer 60 b covers a portion of the side surface of thefirst light emitting cell S1. As shown in FIG. 34 and FIG. 35, theinsulation layer 60 b may extend to a region between the first lightemitting cell S1 and the second light emitting cell S2, and may cover aportion of a side surface of the lower semiconductor layer 55 of thesecond light emitting cell S2. The insulation layer 60 b may be formedof an insulating material, and may particularly include a distributedBragg reflector in which layers having different reflective indexes arealternately stacked. However, the insulation layer 60 b is not limitedthereto. When the insulation layer 60 b includes a distributed Braggreflector, which is multiple layers, it is possible to efficientlysuppress generation of defects such as pinholes in the insulation layer60 b.

The interconnection line 65 electrically connects the first lightemitting cell S1 to the second light emitting cell S2. Theinterconnection line 65 includes a first connection section 65 p and asecond connection section 65 n. The first connection section 65 p iselectrically connected to the transparent electrode layer 61 on thefirst light emitting cell S1, and the second connection section 65 n iselectrically connected to the lower semiconductor layer 55 of the secondlight emitting cell S2. The first connection section 65 p may bedisposed near one edge of the first light emitting cell S1, but is notlimited thereto. In other embodiments, the first connection section 65 pmay be disposed in the central region of the first light emitting cellS1.

The second connection section 65 n may be electrically connected to thelower semiconductor layer 55 of the second light emitting cell S2.Specifically, the second connection section 65 n may be electricallyconnected to the upper surface of the lower semiconductor layer 55 ofthe second light emitting cell S2 through the exposed region R. Further,the first transparent electrode layer 61 may be disposed between thesecond connection section 65 n and the lower semiconductor layer 55 ofthe second light emitting cell S2. In this case, the first transparentelectrode layer 61 may be disposed on a side surface of the lowersemiconductor layer 55 of the second light emitting cell S2, and mayalso be disposed on the exposed region R of the lower semiconductorlayer 55.

The second connection section 65 n may contact the slanted side surfaceof the second light emitting cell S2, more particularly, the slantedside surface of the lower semiconductor layer 55 of the second lightemitting cell S2. Further, as shown in FIG. 34, the second connectionsection 65 n may electrically contact the slanted side surface of thelower semiconductor layer 55 while extending to both sides along thecircumference of the second light emitting cell S2. The first lightemitting cell S1 is connected to the second light emitting cell S2 inseries by the first and second connection sections 65 p, 65 n of theinterconnection line 65.

The interconnection line 65 may contact the transparent electrode layers61, 62 over an overlapping region with the transparent electrode layers61, 62. In the related art, a portion of the insulation layer isdisposed between a transparent electrode layer and an interconnectionline. However, according to an exemplary embodiment of the presentdisclosure, the interconnection line 65 may directly contact thetransparent electrode layers 61, 62 without any insulation materialinterposed therebetween.

With respect to the width of the interconnection line 65, the width of aportion of the first transparent electrode layer 61 disposed on the sidesurface of the lower semiconductor layer 55 of the second light emittingcell S2 may be wider than that of a portion of the interconnection line65 disposed on the side surface of the lower semiconductor layer 55 ofthe second light emitting cell S2. Thus, since a current in a region inwhich the side surface of the second light emitting cell S2 and theinterconnection line 65 contact may be easily distributed, lightemitting uniformity of the MJT LED chip may be improved.

Further, the width of a portion of the first transparent electrode layer61 disposed between the first light emitting cell S1 and the secondlight emitting cell S2 may be wider than that of a portion of theinterconnection line 65 disposed between the first light emitting cellS1 and the second light emitting cell S2. In general, when theinsulation protective layer 63 is etched using an etchant such ashydrofluoric acid, the insulation layer 60 b including an oxide layermay be damaged by the etchant. In this case, since the insulation layer60 b does not insulate the interconnection line 65 from the first lightemitting cell S1, a short-circuit may occur. On the other hand,according to an exemplary embodiment of the present disclosure, sincethe first transparent electrode layer 61 is disposed on the insulationlayer 60 b, and the width of the portion of the first transparentelectrode layer 61 disposed between the first light emitting cell S1 andthe second light emitting cell S2 is wider than that of the portion ofthe interconnection line 65 disposed between the first light emittingcell S1 and the second light emitting cell S2, the insulation layer 60 bdisposed below a transparent conductive layer 62 may be protected frometching damage. Thus, the short-circuit problem by the interconnectionline 65 is prevented.

In FIG. 34, the first connection section 65 p and the second connectionsection 65 n of the interconnection line 65 are connected to each otherthrough two paths. However, it should be understood that the first andsecond connection sections may be connected to each other via a singlepath or more than two paths.

When the insulation layer 60 b has reflective characteristics like thedistributed Bragg reflector, the insulation layer 60 b may be disposedsubstantially in the same region as the region for the interconnectionline 65 within a region having an area of two times or less the area ofthe interconnection line 65. The insulation layer 60 b blocks lightemitted from the active layer 57 from being absorbed into theinterconnection line 65. However, when occupying an excessively largearea, the insulation layer 60 b can block emission of light to theoutside. Thus, there is a need for restriction of the area thereof.

The insulation protective layer 63 may be disposed outside the region ofthe interconnection line 65. The insulation protective layer 63 coversthe first and second light emitting cells S1, S2 outside the region ofthe interconnection line 65. The insulation protective layer 63 may beformed of silicon oxide (SiO₂) or silicon nitride. The insulationprotective layer 63 has an opening through which the transparentelectrode layer 61 on the first light emitting cell S1 and the lowersemiconductor layer of the second light emitting cell S2 are exposed,and the interconnection line 65 may be disposed within the opening.

A side surface of the insulation protective layer 63 and a side surfaceof the interconnection line 65 may face each other, and may also contacteach other. One side surface of the insulation protective layer 63 maybe disposed on the exposed region R and may contact the side surface ofthe interconnection line 65. Unlike this, the side surface of theinsulation protective layer 63 and the side surface of theinterconnection line 65 may be spaced apart from each other while facingeach other.

According to the present embodiment, since the second connection section65 n electrically contacts the upper surface of the lower semiconductorlayer 55, that is, a surface which is not slanted, the second connectionsection 65 n disposed on the upper surface of the lower semiconductorlayer 55 may have a uniform thickness, Thus, reliability of theinterconnection line may be improved. In addition, since the insulationprotective layer 63 contacts the interconnection line 65 on the uppersurface of the lower semiconductor layer 55 which is not slanted withthe side surface of the lower semiconductor layer of the second lightemitting cell S2, an area of an interface between the insulationprotective layer 63 and the interconnection line 65 may be substantiallyconstant. Thus, an error rate of the MJT LED may be reduced.

In addition, the current blocking layer 60 a and the insulation layer 60b may be formed of the same material and have the same structure, andthus may be formed at the same time by the same process. Further, sincethe interconnection line 65 is disposed within the opening of theinsulation protective layer 63, the insulation protective layer 63 andthe interconnection line 65 may be formed using the same mask pattern.

Although two light emitting cells including the first light emittingcell S1 and the second light emitting cell S2 are illustrated in thisexemplary embodiment, it should be understood that the presentdisclosure is not limited thereto. Specifically, a greater number oflight emitting cells may be electrically connected to each other via theinterconnection lines 65. For example, the interconnection lines 65 mayelectrically connect the lower semiconductor layers 55 and thetransparent electrode layers 61 of adjacent light emitting cells to eachother to form a series array of light emitting cells. A plurality ofsuch arrays may be formed and connected inversely parallel to each otherto be operated by an AC power source connected thereto. In addition, abridge rectifier (not shown) may be connected to the series array oflight emitting cells to allow the light emitting cells to be operated bythe AC power source. The bridge rectifier may be formed by bridging thelight emitting cells having the same structure as that of the lightemitting cells S1, S2 using the interconnection lines 65.

As the number of light emitting cells within each of the MJT LEDs isincreased, an area of each of blocks of the printed circuit board may bedecreased. Thus, the backlight unit capable of implementing variouslight emitting arrangements by the plurality of MJT LEDs while reducinga droop phenomenon by more light emitting cells may be provided.

FIG. 36 through FIG. 42 are cross-sectional views illustrating a methodof fabricating an MJT LED chip 123 according to one exemplary embodimentof the present disclosure.

Referring to FIG. 36, a semiconductor stack structure 56 including alower semiconductor layer 55, an active layer 57 and an uppersemiconductor layer 59 is formed on a growth substrate 51. In addition,a buffer layer 53 may be formed on the growth substrate 51 before theformation of the lower semiconductor layer 55.

The growth substrate 51 may be sapphire (Al₂O₃), silicon carbide (SiC),zinc oxide (ZnO), silicon (Si), gallium arsenic (GaAs), galliumphosphide (GaP), lithium alumina (LiAl₂O₃), boron nitride (BN), aluminumnitride (AlN), and gallium nitride (GaN) substrate, without beinglimited thereto. The growth substrate 51 may be selected in various waysdepending upon materials of semiconductor layers to be formed on thegrowth substrate 51. In addition, as shown in FIG. 36, the growthsubstrate 51 may have a convex-concave pattern on an upper surfacethereof as in a patterned sapphire substrate.

The buffer layer 53 is formed to alleviate lattice mismatch between thegrowth substrate 51 and the semiconductor layer 55 formed thereon, andmay be formed of, for example, gallium nitride (GaN) or aluminum nitride(AlN). When the growth substrate 51 is a conductive substrate, thebuffer layer 53 may be formed of an insulation layer or asemi-insulating layer. For example, the buffer layer 53 may be formed ofAlN or semi-insulating GaN.

Each of the lower semiconductor layer 55, the active layer 57 and theupper semiconductor layer 59 may be formed of a gallium nitride-basedsemiconductor material, that is, (Al, In, Ga)N. The lower and uppersemiconductor layers 55, 59 and the active layer 57 may beintermittently or continuously formed by metal organic chemical vapordeposition (MOCVD), molecular beam epitaxy, hydride vapor phase epitaxy(HVPE), and the like.

Here, the upper and lower semiconductor layers may be an n-typesemiconductor layer and a p-type semiconductor layer, respectively, orvice versa. Among the gallium nitride-based compound semiconductorlayers, an n-type semiconductor layer may be formed by doping an n-typeimpurity, for example, silicon (Si), and a p-type semiconductor layermay be formed by doping a p-type impurity, for example, magnesium (Mg).

Referring to FIG. 37, a plurality of light emitting cells S1, S2 spacedapart from each other is formed by a photolithography and etchingprocess. Each of the light emitting cells S1, S2 is formed to have aslanted side surface. Further, in order to partially expose an uppersurface of the lower semiconductor layer 55 of each of the lightemitting cells S1, S2, a photolithography and etching process ofpartially removing the active layer 57 and the upper semiconductor layer59 is added.

Referring to FIG. 38, an insulation layer 60 b partially covering theside surface of the first light emitting cell S1 is formed. Theinsulation layer 60 b may also extend to cover a region between thefirst light emitting cell S1 and the second light emitting cell S2 whilepartially covering a side surface of the lower semiconductor layer 55 ofthe second light emitting cell S2.

The insulation layer 60 b may be formed by depositing an insulationmaterial layer, followed by patterning through the photolithography andetching process. Alternatively, the insulation layer 60 b may be formedof an insulation material layer by a lift-off technique. Particularly,the insulation layer 60 b may be formed of a distributed Bragg reflectorin which layers having different reflective indexes, for example, SiO₂and TiO₂ are alternately stacked. When the insulation layer 60 b isformed of a distributed Bragg reflector, which is multiple layers, it ispossible to suppress generation of defects such as pinholes in theinsulation layer 60 b, whereby the insulation layer 60 b can be formedto have a smaller thickness than that of an insulation layer in therelated art.

Then, the transparent electrode layers 61, 62 are formed on the firstand second light emitting cells S1, S2. The transparent electrode layers61, 62 may be formed of an indium tin oxide (ITO) layer, a conductiveoxide layer such as a zinc oxide layer, or a metal layer such as Ni/Au.The transparent electrode layers 61, 62 are connected to the uppersemiconductor layer 59 and are partially disposed on the insulationlayer 60 b. Further, a portion of the transparent electrode layers 61,62, for example, the first transparent electrode layer 61 may bedisposed between the first light emitting cell S1 and the second lightemitting cell S2, and on the side surface of the lower semiconductorlayer 55 of the second light emitting cell S2. The transparent electrodelayers 61, 62 may be formed by a lift-off process, without being limitedthereto. Alternatively, the transparent electrode layers 61, 62 may beformed by a photolithography and etching process.

Referring to FIG. 10, an insulation protective layer 63 is formed tocover the first and second light emitting cells S1, S2. The insulationprotective layer 63 covers the transparent electrode layers 61, 62 andthe insulation layer 60 b. In addition, the insulation protective layer63 may cover an overall area of the first and second light emittingcells S1, S2. The insulation protective layer 63 may be formed of aninsulation material layer, such as a silicon oxide or silicon nitridelayer, by chemical vapor deposition.

Referring to FIG. 11, a mask pattern 70 having an opening is formed onthe insulation protective layer 63. The opening of the mask pattern 70corresponds to a region for an interconnection line. Then, some regionof the insulation protective layer 63 is removed by etching through themask pattern 70. As a result, an opening is formed on the insulationprotective layer 63 to expose some of the transparent electrode layers61, 62 and the insulation layer 60 b while exposing the exposed region Rof the lower semiconductor layer 55 of the second light emitting cellS2.

Referring to FIG. 41, with the mask pattern 70 remaining on theinsulation protective layer 63, a conductive material is deposited toform the interconnection line 65 within the opening of the mask pattern70. Here, some of the conductive material 65 a may be deposited on themask pattern 70. The conductive material may be deposited by plating,e-beam evaporation, sputtering, or the like.

Referring to FIG. 40, the mask pattern 70, together with some of theconductive material 65 a, is removed from the mask pattern 70. As aresult, the interconnection line 65 electrically connecting the firstand second light emitting cells S1, S2 to each other is completed.

Here, a first connection section 65 p of the interconnection line 65 isconnected to the transparent electrode layer 61 of the first lightemitting cell S1, and a second connection section 65 n thereof isconnected to the upper surface of the lower semiconductor layer 55 ofthe second light emitting cell S2, specifically, the exposed region R.The interconnection line 65 is spaced apart from the side surface of thefirst light emitting cell S1 by the insulation layer 60 b.

In this exemplary embodiment, the current blocking layer 60 a and theinsulation layer 60 b are formed by the same process. As a result, theinsulation protective layer 63 and the interconnection line 65 may beformed using the same mask pattern 70, whereby the MJT LED chip can bemanufactured by the same number of exposure processes while adding thecurrent blocking layer 60 a.

FIG. 42 is a cross-sectional view illustrating an MJT LED chip accordingto another exemplary embodiment of the present disclosure. The MJT LEDchip of FIG. 42 is similar to the MJT LED chip described with referenceto FIG. 35, but has a difference in that it further includes a currentblocking layer 60 a.

The current blocking layer 60 a may be disposed on each of the lightemitting cells S1, S2, and may be disposed between the transparentelectrode layers 61, 62 and the light emitting cells S1, S2.Specifically, the current blocking layer 60 a may be disposed betweenthe first light emitting cell S1 and the first transparent electrodelayer 61, thereby spacing a portion of the first transparent electrodelayer 61 from the first light emitting cell S1. Thus, the transparentelectrode layers 61, 62 are partially disposed on the current blockinglayer 60 a. The current blocking layer 60 a may be disposed near an edgeof each of the light emitting cells S1, S2, but is not limited thereto.The current blocking layer 60 a may also be disposed in the centerregion of each of the light emitting cells S1, S2.

Since a phenomenon in which the current is concentrated around theinterconnection line 65 may be alleviated by the current blocking layer60 a, current distribution efficiency of the MJT LED chip may beimproved.

The current blocking layer 60 a may be formed of an insulating material,and may particularly include a distributed Bragg reflector in whichlayers having different reflective indexes are alternately stacked. Theinsulation layer 60 b may have the same structure as the currentblocking layer 60 a and may be formed of the same material as thecurrent blocking layer 60 a, but is not limited thereto. The insulationlayer 60 b may also be formed of a material different from that of thecurrent blocking layer 60 a by different processes.

The insulation layer 60 b may be connected to the current blocking layer60 a to be continuously disposed, but the present disclosure is notnecessarily limited thereto. The insulation layer 60 b and the currentblocking layer 60 a may be disposed to be spaced apart from each other.

The current blocking layer 60 a may be formed by depositing aninsulation material layer, followed by patterning through thephotolithography and etching process. Alternatively, the currentblocking layer 60 a may be formed of an insulation material layer by alift-off technique. Particularly, the current blocking layer 60 a may beformed of a distributed Bragg reflector in which layers having differentreflective indexes, for example, SiO₂ and TiO₂ are alternately stacked.The current blocking layer 60 a and the insulation layer 60 b may beconnected to each other as shown in FIG. 42, but the present disclosureis not necessarily limited thereto.

The current blocking layer 60 a may be disposed across the entire areain which the interconnection line 65 and the transparent electrodelayers 61, 62 are overlapped with each other. Further, the currentblocking layer 60 a and the insulation layer 60 b may be disposed acrossthe entire area in which the interconnection line 65 and the first lightemitting cell S1 are overlapped with each other.

When the current blocking layer 60 a has reflective characteristics likethe distributed Bragg reflector, the current blocking layer 60 a may bedisposed substantially in the same region as the region for theinterconnection line 65 within a region having an area of two times orless the area of the interconnection line 65. The current blocking layer60 a blocks light emitted from the active layer 57 from being absorbedinto the interconnection line 65. However, when occupying an excessivelylarge area, the current blocking layer 60 a can block emission of lightto the outside. Thus, there is a need for restriction of the areathereof.

Referring to FIG. 42, the transparent electrode layers 61, 62 areconnected to the upper semiconductor layer 59 and are partially disposedon the current blocking layer 60 a and the insulation layer 60 b. Inaddition, the first connection section 65 p of the interconnection line65 may be connected to the first transparent electrode layer 61 withinan upper region of the current blocking layer 60 a.

Structure of Optical Member According to First Embodiment and MJT LEDModule Including the Same

Next, referring to FIG. 3, FIG. 4, and FIG. 19 to FIG. 25, detailedstructures and functions of an optical member according to a firstembodiment and an MJT LED module including the same will be described.

Referring to FIG. 3 again, the optical member 130 according to the firstembodiment may include a lower surface 131 and an upper surface 135, andmay further include a flange 137 and legs 139. The lower surface 131includes a concave section 131 a, and the upper surface 135 includes aconcave surface 135 a and a convex surface 135 b.

The lower surface 131 is composed of a substantially circulardisc-shaped plane, and has the concave section 131 a placed at a centralportion thereof. The lower surface 131 is not required to be a flatsurface, and may have various convex-concave patterns.

Further, an inner surface of the concave section 131 a has a surface 133including side surface 133 a and an upper end surface 133 b. Here, theupper end surface 133 b is perpendicular to a central axis C and theside surface 133 a extends from the upper end surface 133 b to anentrance of the concave section 131 a. Herein, when aligned to coincidewith the optical axis L of the MJT LED 100, the central axis C isdefined as a central axis of the optical member 130, which becomes acenter of a beam distribution of light exiting the optical member 130.

The concave section 131 a may have a shape, a width of which graduallydecreases from the entrance thereof to an upper side thereof.Specifically, the side surface 133 a gradually approaches the centralaxis C from the entrance of the concave section 131 a to the upper endsurface 133 b thereof. With this structure, a region for the upper endsurface 133 b may be formed narrower than the entrance of the concavesection 131 a. The side surface 133 a may have a relatively gentle slopenear the upper end surface 133 b.

The region for the upper end surface 133 b is defined within a narrowerregion than a region for the entrance of the concave section 131 a. Inaddition, the region for the upper end surface 133 b may be definedwithin a narrower region than a region surrounded by an inflection curveat which the concave surface 135 a of the upper surface 135 meets theconvex surface 135 b thereof. Further, the region for the upper endsurface 133 b may be placed within a narrower region than a region forthe cavity 121 a (FIG. 4) of the MJT LED, that is, a light exit region.

The region for the upper end surface 133 b reduces variation of the beamdistribution of light exiting the optical member 130 through the uppersurface 135 thereof even in the case of misalignment between the opticalaxis L of the MJT LED and the central axis C of the optical member 130.Thus, the region for the upper end surface 133 b may be minimized inconsideration of misalignment between the MJT LED 100 and the opticalmember 130.

Further, the upper surface 135 of the optical member 130 includes theconcave surface 135 a and the convex surface 135 b continuouslyextending from the concave surface 135 a with reference to the centralaxis C. A line at which the concave surface 135 a meets the convexsurface 135 b becomes the inflection curve. The concave surface 135 adisperses light exiting near the central axis C of the optical member130 through refraction of the light at a relatively large angle.Further, the convex surface 135 b increases the quantity of lightexiting towards an outer direction of the central axis C.

The upper surface 135 and the concave section 131 a have a symmetricalstructure relative to the central axis C. For example, the upper surface135 and the concave section 131 a have a mirror symmetry structurerelative to a plane passing through the central axis C and may have arotational body shape relative to the central axis C. In addition, theconcave section 131 a and the upper surface 135 may have various shapesaccording to a desired light beam distribution.

In another aspect, the flange 137 connects the upper surface 135 to thelower surface 131 and defines an outer size of the optical member. Aside surface of the flange 137 and the lower surface 131 may be formedwith convex-concave patterns. The legs 139 of the optical member 130 arecoupled to the printed circuit board 110 to support the lower surface131 while separating the lower surface 131 from the printed circuitboard 110. Coupling of the legs 139 to the printed circuit board 110 maybe performed by bonding a distal end of each of the legs 139 to theprinted circuit board 110 using an adhesive or by fitting each of thelegs 139 into a corresponding hole formed in the printed circuit board110.

The optical member 130 is separated from the MJT LED 100, so that an airgap is formed in the concave section 131 a. The housing 121 of the MJTLED 100 is placed below the lower surface 131, and the wavelengthconversion layer 125 of the MJT LED 100 is separated from the concavesection 131 a to be placed under the lower surface 131. With thisstructure, light traveling in the concave section 131 a is preventedfrom being lost due to absorption by the housing 121 or the wavelengthconversion layer 125.

According to this embodiment, when a perpendicular plane relative to thecentral axis C is formed within the concave section 131 a, it ispossible to reduce variation of the beam distribution of light exitingthe optical member 130 even upon misalignment between the MJT LED 100and the optical member 130. Furthermore, since the concave section 131 adoes not have a relatively sharp apex, the optical member can be easilymanufactured.

FIG. 19 shows sectional views of various modifications of the opticalmember. Herein, various modifications of the concave section 131 a shownin FIG. 3 will be described.

In FIG. 19A, the upper end surface 133 b perpendicular to the centralaxis C described in FIG. 3 has a downwardly protruding surface formed ata portion thereof near the central axis C. With this downwardlyprotruding surface, the optical member can achieve primary control oflight entering the portion of the optical member near the central axis Cthereof.

The upper end surface of FIG. 19B is similar to that of FIG. 19A exceptthat the upper end surface of FIG. 19B has upwardly protruding surfacesformed at portions thereof perpendicular to the central axis C of theoptical member. Since the upper end surface is combined with theupwardly protruding surfaces and the downwardly protruding surface, theoptical member can reduce variation in light beam distribution due tomisalignment between the MJT LED and the optical member.

The upper end surface of FIG. 19C is different from that of FIG. 3 inthat the upper end surface 133 b is formed with an upwardly protrudingsurface at a portion thereof near the central axis C of the opticalmember. With this upwardly protruding surface, the optical member canachieve further dispersion of light entering the portion of the opticalmember near the central axis C thereof.

The upper end surface of FIG. 19D is similar to that of FIG. 19C exceptthat the upper end surface has downwardly protruding surfaces atportions thereof perpendicular to the central axis C of the opticalmember. Since the upper end surface is combined with the upwardlyprotruding surfaces and the downwardly protruding surface, the opticalmember can reduce variation in light beam distribution due tomisalignment between the MJT LED and the optical member.

FIG. 20 shows sectional views of an optical member, illustrating an MJTLED module according to a further exemplary embodiment of the presentdisclosure.

Referring to FIG. 20A, the upper end surface 133 b may be formed with alight scattering pattern 133 c. The light scattering pattern 133 c maybe a convex-concave pattern. In addition, the concave surface 135 a mayalso be formed with a light scattering pattern 135 c. The lightscattering pattern 135 c may also be a convex-concave pattern.

Generally, a relatively large luminous flux is concentrated near thecentral axis C of the optical member. Furthermore, according toembodiments of the present disclosure, since the upper end surface 133 bis perpendicular to the central axis C, more luminous flux can beconcentrated near the central axis C. Accordingly, with the structure ofthe upper end surface 133 b and/or the concave surface 135 a having thelight scattering patterns 133 c, 135 c, it is possible to disperseluminous flux near the central axis C of the optical member.

Referring to FIG. 20B, a material layer 139 a having a different indexof refraction than that of the optical member 130 may be placed on theupper end surface 133 b. The index of refraction of the material layer139 a may be higher than that of the optical member, thereby allowingchange of an optical path of light incident on the upper end surface 133b.

Further, a material layer 139 b having a different index of refractionthan that of the optical member 130 may also be placed on the concavesurface 135 a. The index of refraction of the material layer 139 b maybe higher than that of the optical member, thereby allowing change of anoptical path of light exiting through the concave surface 135 a.

The light scattering patterns 133 c, 135 c of FIG. 20A and the materiallayers 139 a, 139 b of FIG. 20B may also be applied to the variousoptical members of FIG. 19.

FIG. 21 is a sectional view illustrating dimensions of an MJT LED moduleused for simulation. Here, the same reference numerals as those of FIGS.3 and 4 are used (please also refer to FIGS. 3 and 4 for a depiction ofsome elements).

In the MJT LED 100, the cavity 121 a has a diameter of 2.1 mm and aheight of 0.6 mm. The wavelength conversion layer 125 fills the cavity121 a and has a flat surface. A distance (d) between the MJT LED 100 andthe lower surface 131 of the optical member 130 is 0.18 mm and the MJTLED 100 and the optical member 130 are arranged such that the opticalaxis L of the MJT LED 100 is aligned with the central axis C of theoptical member.

The optical member 130 has a height (H) of 4.7 mm and an upper surfaceof the optical member has a width (W1) of 15 mm. The concave surface 135a has a width (W2) of 4.3 mm. Further, the entrance of the concavesection 131 a placed on the lower surface 131 has a width (w1) of 2.3mm, and the upper end surface 133 b has a width (w2) of 0.5 mm. Theconcave section 131 a has a height (h) of 1.8 mm.

FIGS. 22A, 22B, and 22C show graphs depicting a shape of the opticalmember of FIG. 21. Here, FIG. 22A is a sectional view of the opticalmember illustrating reference point P, distance R, angle of incidenceθ1, and exit angle θ5; FIG. 22B shows variation of distance R accordingto angle of incidence θ1; and FIG. 22C shows variation of θ5/θ1according to angle of incidence θ1. FIG. 23 shows traveling directionsof light beams entering the optical member 130 from reference point P atintervals of 3°.

Referring to FIG. 22A, reference point P indicates a light exit point ofthe MJT LED 100 placed on the optical axis L. Properly, reference pointP is set to be placed on an outer surface of the wavelength conversionlayer 125 in order to exclude external factors, such as light scatteringby the phosphors in the MJT LED 100 and the like.

θ1 indicates an angle of incidence of light entering the optical member130 from the reference point P, and θ5 indicates an exit angle of lightexiting the optical member 130 through the upper surface 135 thereof. Rindicates a distance from reference point P to the inner surface of theconcave section 131 a.

Referring to FIG. 22B, since the upper end surface 133 b of the concavesection 131 a is perpendicular to the central axis C, R slightlyincreases with increasing θ1. An enlarged graph in FIG. 22B shows anincreasing curve of R. On the side surface 133 a of the concave section131 a, R decreases with increasing θ1 and slightly increases near theentrance of the concave section 131 a.

Referring to FIG. 22C, as θ1 increases, θ5/θ1 rapidly increases near theconcave surface 135 a and relatively gently decreases near the convexsurface 135 b. In this embodiment, as shown in FIG. 23, luminous fluxexiting the optical member through the concave surface 135 a thereof mayoverlap luminous flux exiting the optical member through the convexsurface 135 b thereof. That is, among light beams entering the opticalmember from reference point P, light exiting the optical member throughthe concave surface 135 a near the inflection curve may have a higherrefraction angle than light exiting the optical member through theconvex surface 135 b. Thus, it is possible to reduce concentration ofluminous flux near the central axis C by forming the upper end surface133 b of the concave section 131 a to have a planar shape and adjustingthe shapes of the concave surface 135 a and the convex surface 135 b.

FIGS. 24A and 24B shows graphs depicting illuminance distribution.Specifically, FIG. 24A is a graph depicting illuminance distribution ofan MJT LED, and FIG. 24B is a graph showing illuminance distribution ofthe MJT LED module using an optical member. Illuminance distribution isrepresented as a magnitude of luminous flux density of light entering ascreen separated a distance of 25 mm from a reference point.

As shown in FIG. 24A, the MJT LED 100 provides a bilaterally symmetricillumination distribution with reference to the optical axis (C), andhas a luminous flux density which is very high at the center thereof andrapidly decreases towards the periphery thereof. When the optical member130 is applied to the MJT LED 100, the MJT LED 100 can provide asubstantially uniform luminous flux density within a radius of 40 mm, asshown in FIG. 24B.

FIGS. 25A and 25B show graphs depicting light beam distributions.Specifically, FIG. 25A is a graph depicting a light beam distribution ofan MJT LED, and FIG. 25B is a graph depicting a light beam distributionof the MJT LED module using an optical member. The light beamdistribution shows light intensity at a place separated a distance of 5m from reference point P according to a beam angle, and beamdistributions in orthogonal directions are shown to overlap each otherin one graph.

As shown in FIG. 25A, the intensity of light emitted from the MJT LED100 is high at a beam angle of 0°, that is, at the center thereof, andgradually decreases with increasing beam angle. When the optical memberis applied to the MJT LED 100, the intensity of light emitted from theMJT LED 100 is relatively low at a beam angle of 0° and is relativelyhigh near a beam angle of 70°, as shown in FIG. 25B.

Accordingly, when the optical member 130 is applied to the MJT LED 100,it is possible to achieve uniform backlighting of a relatively wide areathrough change of the light beam distribution of the MJT LED, which hashigh light intensity at the center thereof.

Structure of Optical Member According to Second Embodiment and MJT LEDModule Including the Same

Next, referring to FIG. 26 to FIG. 33B, detailed structures andfunctions of an optical member according to a second embodiment and anMJT LED module including the same will be described.

FIG. 26 is a sectional view of an MJT LED module according to oneexemplary embodiment of the present disclosure, and FIG. 27A, FIG. 27Band FIG. 27C are sectional views of the MJT LED module taken along linesa-a, b-b and c-c of FIG. 26. Here, line a-a corresponds to a line on alower surface of the optical member, line c-c corresponds to a line onan upper surface of the optical member, and line b-b corresponds to acutting line at the middle of the height of a diffusion lens betweenline a-a and line c-c. Further, FIG. 28 is a detailed view of an opticalmember of the MJT LED module shown in FIG. 26, and FIG. 29 shows a lightbeam angle distribution of the MJT LED module using the optical memberof FIG. 28.

Referring to FIG. 26, the MJT LED module includes an MJT LED 100 and anoptical member 230 disposed on the MJT LED 100 and formed of a resin orglass material. Although the printed circuit board 110 is partiallyshown to show a single MJT LED module in this embodiment, a plurality ofMJT LED modules is regularly arranged on a single printed circuit board110 to form the backlight module 300 as described above.

First, the MJT LED 100 and the printed circuit board 110 are the same asthose of the first embodiment described above with reference to FIG. 3and FIG. 4, and detailed descriptions thereof will be omitted. Thus, theoptical member 230 according to the second embodiment will be mainlydescribed hereinafter.

Referring to FIG. 26, the optical member 230 includes a lower surface231 and a light exit face 235 at the opposite side thereof, and mayfurther include legs 239. The lower surface 231 includes a concave lightincident section 231 a. The light exit face 235 is generally composed ofan upwardly protruding round surface, and includes a flat surface 235 aformed at an upper center thereof. The flat surface 235 a is placedcorresponding to a concave section of an optical member such as aspectsof the optical member shown in the first embodiment, and the opticalmember 230 according to the present embodiment can disperse light nearthe optical axis by the structure of a light incident section 231 adescribed in detail hereinafter even without the concave section at theupper center of the light exit face. The light incident section 231 ahas a substantially bell-shaped cross-section. That is, the lightincident section 231 a has a shape which gradually converges from alower entrance thereof adjacent the MJT LED 100 towards an upper apexthereof.

Referring to FIG. 27A, the lower surface 231 of the optical member 230has a circular shape. In addition, the light incident section 231 a hasa lower portion placed at a center of the lower surface 231, and thelower portion of the light incident section 231 a has a circular shape.The light incident section 231 a maintains a circular shape from thelower entrance immediately before the upper apex thereof, and has agradually decreasing diameter in an upward direction. Referring to FIG.27C, the upper flat surface 235 a of the optical member 230 also has acircular shape.

Referring to FIG. 27A, FIG. 27B and FIG. 27C in order, the opticalmember 230 includes the lower surface 231 having a circular shape, andhas a gradually decreasing diameter in the upward direction. The opticalmember 230 may have a greater variation in diameter of a circular outercircumference at an upper portion of a side surface thereof than that ofthe circular outer circumference at a lower portion of the side surfacethereof. The circular shape of the light incident section 231 a has agradually decreasing diameter.

Referring to FIG. 28, an optical axis L corresponding to the centralaxis of the optical member 230 is shown. To obtain a uniform lightdistribution using the optical member 230, it is necessary to have alight intensity peak at an angle of 60° or more from the optical axis L.To obtain such optical characteristics, it is important to achieveeffective dispersion of light at an angle of 50° or less from theoptical axis L. FIG. 28 shows reference line (r) at an angle of 50° orless relative to the optical axis L.

To achieve effective dispersion of light at an angle of 50° or less fromthe optical axis L, within the range between the optical axis L and thereference line (r), that is, at an angle of 50° or less from the opticalaxis L, the shortest distance ‘b’ from a certain point (p) on theoptical axis L to the apex of the light incident section 231 a isgreater than the shortest distance ‘a’ from the point (p) to the sidesurface of the light incident section 231 a. As above, when b>a, thelight incident section 231 a can contribute to wide dispersion of lighttraveling within an angle of 50° or less from the optical axis L to anangle of 60° or more from the optical axis L. In contrast, when b<a, thelight incident section 231 a fails to contribution to wide dispersion oflight traveling within an angle of 50° or less from the optical axis L.As such, it is necessary to form a separate concave section for widedispersion of light at the upper center of the light exit face in therelated art. In other words, the optical member 230 according to thepresent disclosure employs the curved structure of the light incidentsection 231 a satisfying the condition of b>a within an angle of 50° orless from the optical axis L and thus the concave section at the uppercenter of the light exit face can be omitted.

Here, the light incident section 231 a preferably has a height greaterthan a radius R of the lower entrance of the light incident section 231a. More preferably, the height H of the light incident section 231 a is1.5 times or more the radius R thereof. In addition, a lower portion ofthe light incident section 231 a adjoins air which has a lower index ofrefraction than the resin or glass material, and an upper portion of thelight exit face also adjoins air which has a lower index of refractionthan the resin or glass material.

FIG. 29 shows a light beam angle distribution of the MJT LED moduleusing the optical member of FIG. 28. Referring to FIG. 29, it can beseen that a light intensity peak is formed at about 72° from the opticalaxis L and light is widely distributed. From the result of FIG. 29, itcan be seen that the optical member 230 according to the presentdisclosure can uniformly disperse light at an angle of 60° or less fromthe optical axis L through the curved structure of the light incidentsection 231 a satisfying the condition of b>a at an angle of 50° or lessfrom the optical axis L even without the concave section at the uppercenter of the light exit face, thereby achieving uniform distribution oflight.

FIG. 30 is a sectional view of an optical member according to anotherexemplary embodiment of the present disclosure. As clearly shown in FIG.30, the optical member 230 according to this embodiment has the samecurved structure of the light incident section 231 a as that of theoptical member shown in FIG. 28. Thus, the light incident section 231 aof the optical member according to this embodiment satisfies thecondition of b>a at an angle of 50° or less from the optical axis L.Here, unlike the optical member according to the above embodiment, whichhas the flat surface formed at the upper center of the light exit face,the optical member 230 according to this embodiment has a convexly roundsurface 235 b at the upper center of the light exit face.

FIG. 31 clearly shows a beam angle distribution curve of an MJT LEDmodule using the optical member of FIG. 30. Referring to FIG. 31, it canbe seen that a light intensity peak is formed at about 72° from theoptical axis L and light is widely distributed. In addition, there is nosignificant difference between the light beam angle distribution of FIG.31 and the light beam angle distribution of FIG. 29. Thus, it can beseen that, when the light incident section 231 a satisfies the conditionof b>a at an angle of 50° or less from the optical axis L, there is nosignificant difference in light beam angle distribution, regardless ofwhether the light exit face has the flat surface or the convex surfaceat the upper center thereof.

FIGS. 32A and 32B show an optical member according to ComparativeExample 1 and a beam angle distribution curve thereof.

In the optical member of FIG. 32A, at an angle of 50° or less from theoptical axis L, the shortest distance ‘b’ from a certain point on theoptical axis to an apex of a light incident section is greater than theshortest distance ‘a’ from the same point to a side surface of the lightincident section, and the light exit face has a concave section formedat an upper center thereof. In FIG. 32B showing a beam angledistribution curve under these conditions, it can be seen that there isno substantial difference in light beam angle distribution between theabove embodiments and this comparative example. This result means that,under the condition of b>a, the concave section formed at the uppercenter of the light exit face provides substantially no function inchange of the light beam angle distribution.

FIGS. 33A and B show an optical member according to Comparative Example2 and a light beam angle distribution thereof.

In the optical member of FIG. 33A, at an angle of 50° or less from theoptical axis L, the shortest distance ‘b’ from a certain point on theoptical axis to an apex of a light incident section is smaller than theshortest distance ‘a’ from the same point to a side surface of the lightincident section, and the light exit face has a concave section formedat an upper center thereof. In FIG. 33B showing a beam angledistribution curve under these conditions, it can be seen that there isno substantial difference between the light beam angle distribution ofComparative Example 1 and that of the above embodiments. This resultmeans that, under the condition of b<a, the concave section formed atthe upper center of the light exit face contributes to wide dispersionof light at an angle of 50° or less from the optical axis L.

Although the present disclosure has been illustrated with reference tosome exemplary embodiments in conjunction with the drawings, it shouldbe understood that some features of a certain embodiment may also beapplied to other embodiments without departing from the spirit and scopeof the disclosure. Further, it should be understood that theseembodiments are provided by way of illustration only, and that variousmodifications and changes can be made without departing from the spiritand scope of the present disclosure.

FIG. 43A and FIG. 43B are schematic views comparing a backlight unit(FIG. 43A) in the related art with a backlight unit (FIG. 43B) accordingto one exemplary embodiment of the present disclosure.

Referring to FIG. 43A, the backlight unit in the related art includes aplurality of LED chips having a single light emitting cell, and theplurality of LED chips are connected to each other in series and/or inparallel to form one or more arrays 110 a, thereby enabling an operationin a unit of each array 110 a. On the other hand, in the backlight unitillustrated in FIG. 43B according to one exemplary embodiment of thepresent disclosure, MJT LEDs may be independently operated without beingconnected to each other in series, in parallel, or in series/parallel.As a result, for example, the backlight unit in the related art may have9 arrays 110 a, while the backlight unit according to the presentdisclosure may include 45 blocks.

Depending on the configuration difference as described above, thefollowing effect difference exhibits. It is assumed that the backlightunit in the related art of FIG. 43A is Comparative example, and thebacklight unit according to the present disclosure of FIG. 43B is one ofInventive examples. All of the backlight units of Comparative exampleand the Inventive example have been operated at a DC converter voltageof 24V, and an IC operating voltage was 3V. An operating voltage of anLED chip of a single light emitting cell of Comparative example was3.6V, and a loss voltage of each array was 3V. In addition, an operatingvoltage of one MJT LED of the Inventive example was 3.3V, and a lossvoltage of each block 110 b was 1.2V.

The backlight unit of Comparative example may be operated at 0.4 A, andthe backlight unit of the Inventive example may be operated at 0.075 A.As a result, the droop phenomenon occurring at high current may bereduced. In addition, since operation power of Comparative example is75.6 W, and operating power of the Inventive example is 70.87 W, losspower of Comparative example was 10.8 W and loss power of Inventiveexample was 4.05 W, and operating efficiency calculated based on thosedescribed above was 85.7% (Comparative example) and 94.2% (Inventiveexample), respectively. Thus, it may be confirmed that the operatingefficiency of the backlight unit according to the present disclosure ishigher than that of the related art.

According to one or more exemplary embodiments of the presentdisclosure, the backlight module is fabricated using the MJT LEDs havinglow current operation characteristics, thereby enabling low currentoperation of the backlight module and the backlight unit including thesame.

In addition, according to one or more exemplary embodiments of thepresent disclosure, one connection section of the interconnection lineelectrically contacts a slanted side surface of the light emitting cell,thereby increasing an effective light emitting area of each of lightemitting cells in an MJT LED chip.

Further, according to one or more exemplary embodiments of the presentdisclosure, it is possible to enhance stability and reliability of drivecircuits for controlling operation of the backlight module whilereducing manufacturing costs.

Further, according to one or more exemplary embodiments of the presentdisclosure, the backlight unit has improved power efficiency andluminous efficacy, and can prevent a droop phenomenon due to operationat high current.

Further, according to one or more exemplary embodiments of the presentdisclosure, it is possible to minimize or reduce the number of LEDsconstituting the backlight module and to allow an individual operationof the MJT LEDs constituting the backlight module.

What is claimed is:
 1. A backlight unit, comprising a backlight module,comprising: a printed circuit board comprising blocks; and lightemitting diode (LED) chips disposed on the blocks; and a backlightcontrol module configured to perform a dimming control of the LED chips,wherein each of the LED chips comprises: light emitting cells spacedapart from each other, each of the light emitting cells comprising alower semiconductor layer, an upper semiconductor layer disposed on thelower semiconductor layer, and an active layer disposed between thelower and upper semiconductor layers, the lower semiconductor layers ofthe light emitting cells being partially exposed; connection structureselectrically connecting the light emitting cells to each other, each ofthe connection structures electrically connecting an upper semiconductorlayer of one light emitting cell to a lower semiconductor layer ofanother light emitting cell; and an insulation layer disposed betweenthe light emitting cells and the connection structures, the insulationlayer covering a portion of the exposed lower semiconductor layers andhaving a width wider than the connection structures.
 2. The backlightunit of claim 1, wherein: each of the light emitting cells comprisesfirst to N^(th) light emitting cells, N is a natural number of 2 orgreater; and a connection structure for electrical connection betweenthe N^(th) light emitting cell and an N-1^(th) light emitting cell isthe same as that between the first light emitting cell and a secondlight emitting cell.
 3. The backlight unit of claim 2, wherein each ofthe LED chips further comprises a single substrate on which the lightemitting cells are disposed.
 4. The backlight unit of claim 3, wherein:a surface of the single substrate is exposed between two light emittingcells; and the insulation layer covers the exposed surface of the singlesubstrate.
 5. The backlight unit of claim 4, wherein each of theconnection structure comprises an interconnection line.
 6. The backlightunit of claim 1, wherein each of the LED chips further comprises:transparent electrode layers disposed on the light emitting cells andcontacting the upper semiconductor layers; and an insulation protectivelayers covering the transparent electrode layers, the insulationprotective layers having openings exposing the transparent electrodelayers.
 7. The backlight unit of claim 2, wherein: the lowersemiconductor layer of an M^(th) light emitting cell is electricallyconnected to the upper semiconductor layer of an M-1^(th) light emittingcell; and M is a natural number of 2 or greater, and less than or equalto N.
 8. The backlight unit of claim 1, wherein the backlight controlmodule comprises: an operation power generator configured to provide anoperating voltage to the LED chips; and an operation controllerconfigured to independently control a dimming level of each of theblocks.
 9. The backlight unit of claim 8, wherein: each of the blockscomprises an anode terminal and a cathode terminal; and the anodeterminal of each of the blocks is directly connected to the operationpower generator and the cathode terminal of each of the blocks isdirectly connected to the operation controller.
 10. The backlight unitof claim 9, wherein: an operating voltage of each of the blocks is in arange of about to 6V to about to 36V; and an operating current of eachof the blocks is equal to or less than 125 mA.
 11. The backlight unit ofclaim 1, further comprising optical members disposed on the LED chips,each of the optical members being configured to change a light beamdistribution of a corresponding LED chip.
 12. The backlight unit ofclaim 11, wherein each of the optical members is disposed directly oneach of the LED chips.
 13. A display device, comprising: a liquidcrystal panel; and a direct type backlight unit disposed under theliquid crystal panel, the direct type backlight unit comprising: abacklight module, comprising: a printed circuit board comprising blocks;and light emitting diode (LED) chips disposed on the blocks; and abacklight control module configured to perform a dimming control of theLED chips, wherein each of the LED chips comprises: light emitting cellsspaced apart from each other, each of the light emitting cellscomprising a lower semiconductor layer, an upper semiconductor layerdisposed on the lower semiconductor layer, and an active layer disposedbetween the lower and upper semiconductor layers, the lowersemiconductor layers being partially exposed; connection structureselectrically connecting the light emitting cells to each other, each ofthe connection structures electrically connecting an upper semiconductorlayer of one light emitting cell to a lower semiconductor layer ofanother light emitting cell; and an insulation layer disposed betweenthe light emitting cells and the connection structures, the insulationlayer covering a portion of the exposed lower semiconductor layers andhaving a width wider than the connection structures.
 14. The displaydevice of claim 13, wherein: each of the light emitting cells comprisesfirst to N^(th) light emitting cells, N is a natural number of 2 orgreater; and a connection structure for electrical connection betweenthe N^(th) light emitting cell and an N-1^(th) light emitting cell isthe same as that between the first light emitting cell and a secondlight emitting cell.
 15. The display device of claim 14, wherein each ofthe LED chips further comprises a single substrate on which the lightemitting cells are disposed.
 16. The display device of claim 13, whereinthe backlight control module comprises: an operation power generatorconfigured to provide an operating voltage to the LED chips; and anoperation controller configured to independently control a dimming levelof each of the blocks.
 17. The display device of claim 16, wherein: eachof the blocks comprises an anode terminal and a cathode terminal; andthe anode terminal of each of the blocks is directly connected to theoperation power generator and the cathode terminal of each of the blocksis directly connected to the operation controller.
 18. The displaydevice of claim 13, wherein each of the LED chips further comprises:transparent electrode layers disposed on the light emitting cells andcontacting the upper semiconductor layers; and an insulation protectivelayers covering the transparent electrode layers, the insulationprotective layers having openings exposing the transparent electrodelayers.